BAGHDAD - President Bush called a crackdown on Shiite militias critical to success in Iraq, but Prime Minister Nouri al-Maliki has been noticeably silent, perhaps because his public support for Bush's plan would mean endorsing attacks on the Shiite radicals who helped him into office.

The Americans insist Maliki vowed not to interfere this time around, a third attempt since the prime minister took power in May to cleanse the capital of militant gunmen, whether Sunni insurgents or Shiite militiamen.

In announcing a new Iraq policy Wednesday night, Bush said earlier efforts to tame the sectarian bloodshed in Baghdad had been snarled by "political and sectarian interference [that] prevented Iraqi and American forces from going into neighborhoods that are home to those fueling the sectarian violence."

"This time, Iraqi and American forces will have a green light to enter those neighborhoods," Bush said. "Prime Minister Maliki has pledged that political or sectarian interference will not be tolerated."

However, Maliki, a Shiite, so far has studiously avoided confirming that pledge in public, sticking instead to utterances that anyone illegally carrying weapons would be dealt with harshly.

In announcing his version of the new security plan last Saturday, Maliki said it "will not provide a safe haven for any outlaws, regardless of sectarian or political affiliation."

But he has been saying that to Iraqis for months, even as he ordered U.S. forces in October to stop all attacks on Baghdad's Sadr City neighborhood, headquarters of the Mahdi Army militia of his key political backer, radical Shiite cleric Muqtada al-Sadr. Maliki said he should approve all operations first.

In the same period, he forced U.S. troops to end a blockade of the northeast Baghdad Shiite slum where the Americans were searching for a still-missing kidnapped soldier.

Richard N. Haass, president of the Council on Foreign Relations, said he doubted Maliki intended to change his highly sectarian policies.

"I just don't see evidence that either Mr. Maliki or those around him are both willing and able to act as truly national figures, which would require them to provide a lot more political and economic space for the Sunnis and demand that the Shiite militias disband," Haass said on the organization's Web site.

Beyond that, the Bush troop increase, while a symbolic move, would make little difference, Haass said.

"If the Iraqis were really prepared to do what needs doing, additional U.S. troops would not be necessary," said Haass, who was an adviser to former Secretary of State Colin L. Powell. "And if the Iraqis are not prepared to do what needs doing, this sort of increase won't be enough."

Muqtedar Khan, a senior fellow at the Saban Center for Middle East Policy at the Brookings Institution, also did not put much stock in Maliki's promise to crack down on Shiite militias. Khan said he suspected the Iraqi leader was simply trying to placate the Americans, whom, it seems, he cannot live with or without.

"This is the kind of game most global politicians are born with," said Khan, who is also a professor of Islam and global studies at the University of Delaware. "It's called managing Washington."

Sadr's office yesterday said the troop buildup was doomed.

"We reject Bush's new strategy, and we think it will fail," said Abdul-Razzaq al-Nidawi, a senior official in Sadr's office in the Shiite holy city of Najaf.

"We call upon the American people to oppose sending more of their sons to Iraq so that they will not be flown back in coffins," he said.