BAGHDAD, Oct. 31 — Prime Minister Nuri Kamal al-Maliki demanded the removal of American checkpoints from the streets of Baghdad on Tuesday, in what appeared to be his latest and boldest gambit in an increasingly tense struggle for more independence from his American protectors.

Mr. Maliki’s public declaration seemed at first to catch American commanders off guard. But by nightfall, American troops had abandoned all the positions in eastern and central Baghdad that they had set up last week with Iraqi forces as part of a search for a missing American soldier. The checkpoints had snarled traffic and disrupted daily life and commerce throughout the eastern part of the city.

The language of the declaration, which implied that Mr. Maliki had the power to command American forces, seemed to overstep his authority and to be aimed at placating his Shiite constituency.

The withdrawal was greeted with jubilation in the streets of Sadr City, the densely populated Shiite enclave where the Americans have focused their manhunt and where anti-American sentiment runs high. The initial American reaction to the order, which was released by Mr. Maliki’s press office, strongly suggested that the statement had not been issued in concert with the American authorities.

“Our commanders have his press release and are reviewing how best to address these concerns,” Lt. Col. Christopher Garver, a military spokesman in Baghdad, said early Tuesday afternoon, about an hour after the order was issued.

Late Tuesday night, after hours of silence, a senior American Embassy official who had been delegated to return reporters’ phone calls said the prime minister’s order was “the result of a meeting” between Mr. Maliki, Ambassador Zalmay Khalilzad and Gen. George W. Casey Jr., the top American commander in Iraq. “It was essentially something that Maliki wanted to do and Casey agreed to it,” the official said.

But Mr. Maliki’s announcement may have been a foregone conclusion: the meeting was at 1 p.m., officials said, and the prime minister’s office issued his press release at about 1:20 p.m.

Tensions between Mr. Maliki and President Bush have been building for months. American officials have grown impatient with the Iraqi government’s inability to curb Shiite militias accused of sectarian killings and to reduce the insurgent violence. For their part, Mr. Maliki and other leading Shiites have begun to chafe at American control of the military and what they view as American favoritism toward Sunnis.

Those tensions erupted publicly last week, to be followed by shows of reconciliation.

On Wednesday, Mr. Maliki challenged an American assertion that the two governments had agreed on a timetable for stabilizing Iraq. On Thursday and Friday, he issued angry comments pointedly voicing his independence from the Americans, including an account circulated by his aide of an acrimonious meeting with Mr. Khalilzad, during which Mr. Maliki was said to have told the ambassador that he was “a friend of the United States, but not America’s man in Iraq.” On Saturday, the White House convened a videoconference at which Mr. Maliki publicly praised President Bush.

The abrupt declaration by Mr. Maliki on Tuesday followed a visit to Baghdad on Monday by President Bush’s national security adviser, Stephen J. Hadley, who was here to discuss how to reverse the country’s slide toward all-out civil war.

Violence continued to torment the country on Tuesday, including the mass kidnapping of at least 50 civilians by gunmen on a road north of Baghdad, and the announcement that 2 more American troops had been killed, raising the toll of American deaths this month to at least 103.

Mr. Maliki had been under pressure from his Shiite backers to push the Americans to lift an eight-day-old cordon around Sadr City, where American authorities believe the kidnapped American soldier is being held.

The soldier was abducted in the central Baghdad neighborhood of Karada on Oct. 23 after leaving the fortified Green Zone without authorization. Three people were detained early Tuesday in the latest raid in Sadr City as part of the manhunt, the American military said. Although the military has not released the name of the soldier, members of an Iraqi family who said they were the missing soldier’s in-laws identified him as Ahmed Qusai al-Taei, 41.

Moktada al-Sadr, the powerful Shiite cleric who counts Sadr City as his greatest bastion of support and who wields considerable influence in Mr. Maliki’s ruling Shiite coalition, called for a general strike in the neighborhood on Tuesday to protest the cordon. In its search for the soldier, the American military has singled out the Mahdi Army militia, which has grown increasingly fractured but still answers in part to Mr. Sadr.

Joint American-Iraqi roadblocks and checkpoints at the entrances to the neighborhood, and others erected in Karada, have caused major traffic jams, impeded commerce, turned short commutes into ordeals lasting hours and provoked the ire of Iraqis. On Monday, Mr. Sadr, who led two uprisings against American troops in 2004, threatened unspecified action if the American “siege” continued.

The wording of Mr. Maliki’s statement on Tuesday seemed intended to curry political favor with the residents and power brokers of Sadr City. “Mr. Nuri al-Maliki, the general commander of the armed forces, has issued an order to remove all barriers and checkpoints and open all entrances in Sadr City and all other areas in Baghdad and ease traffic jams in these areas no later than 5 p.m. today,” it said.

Under United Nations resolutions that remain in effect, the American military exercises control over American troops in Iraq, but consults closely with the Iraqi government as a partner. For that reason, the declaration appeared to be as much about Mr. Maliki’s stagecraft as about practical effects on the ground.

Within an hour of the statement, American troops had already begun pulling away from the checkpoints on the edge of Sadr City, according to witnesses, though Iraqi security forces remained behind. Lt. Col. Jonathan B. Withington, a military spokesman in Baghdad, said the order would affect only the checkpoints established in the last week, not all the checkpoints manned by Iraqi security forces.

When asked whether the American withdrawal was a response to the prime minister’s statement, Colonel Withington chose his words carefully: “We were ordered by our military chain of command not to impede traffic” in Karada and on the eastern access roads to Sadr City, he said.

The country’s Sunni leadership condemned Mr. Maliki’s decision, saying it would upend the Baghdad security plan and expose the population to greater violence. General Casey said last week that Iraqi security forces still needed at least a year before they would be ready to take over full control of the country’s security.

Tariq al-Hashemi, one of Iraq’s two vice-presidents and the leader of the largest Sunni Arab bloc, said the prime minister’s decision “will allow the terrorists and the insurgents to move freely.” He said that civilians’ lives should be more important than saving a few hours during a commute.

A National Police officer posted at a checkpoint near the Habibiya Bridge entrance to Sadr City said the departure of the Americans, who had left 15 minutes earlier, would make his job more difficult. “They helped us to stop everyone,” said the officer, who gave only his first name, Salam. “If we are alone, we can’t say a word against certain people.”

Mr. Maliki’s order said that special security measures, such as the latest roadblocks, “will be carried out only during the curfew period and in emergencies.” It added: “Joint efforts to track down the terrorists and outlaws who jeopardize the lives of people by killing and kidnapping will continue.”

According to senior Shiite politicians close to Mr. Maliki, the Americans had been extremely reluctant, if not opposed, to withdrawing from their roadblocks and checkpoints in Karada and Sadr City.

Ali al-Adeeb, a Shiite member of Parliament and a senior member of Mr. Maliki’s Islamic Dawa Party, said the prime minister had discussed the matter of the roadblocks with American officials during the past several days. In a meeting on Monday, Mr. Adeeb said, American officials had asked Mr. Maliki to give them 72 hours before issuing his order.

Hassan al-Sined, an adviser to the prime minister and a senior Dawa Party member, said he doubted that the order was coordinated with the Americans. “I don’t think he got the Americans’ opinion,” Mr. Sined said, though he said he was not privy to details of Tuesday’s meeting.

If the declaration was intended to show Mr. Maliki as a forceful and decisive leader, as far Mr. Sined was concerned, it had that effect. The order demonstrated that Mr. Maliki was “a strong and brave prime minister,” he said. “He behaved like a successful prime minister.”

The senior American Embassy official said that the embassy applauded the boldness of Mr. Maliki’s declaration. “We’re actually encouraging the prime minister to take responsibility,” he said. “So trying to sound like he’s a leader here in Iraq is a good thing.”

Mr. Maliki was not available for comment and his spokesman, who is the only administration official authorized to speak on the prime minister’s behalf, was in Kuwait on Thursday. When contacted by telephone late Tuesday, the spokesman said he had only just heard about Mr. Maliki’s order and could offer no details.

The victims of the mass kidnapping north of Baghdad on Tuesday were mostly Shiites and were ambushed by gunmen as they traveled in cars along a road from the capital to Balad, according to an official in the news media office of Salahuddin Province, north of Baghdad. The gunmen stopped the cars and scrutinized the occupants’ identification before abducting the victims, the official said.

The American military announced that two soldiers died in Baghdad on Monday, one when a bomb exploded next to his vehicle and the other by small arms fire. With at least 103 announced deaths, October has been the fourth-deadliest month for American troops since the beginning of the war. The other highest monthly tolls were 107 in January 2005, 135 in April 2004, and 137 in November 2004.

Abdul Razzaq al-Saiedi and Omar al-Neami contributed reporting from Baghdad, and an Iraqi employee of The New York Times from Dhuluiya.