President Bush is frustrated, his ambassador to Baghdad is disappointed. But there are no ready alternatives to Iraqi Prime Minister Nouri al-Maliki, and his opponents lack the votes to replace him.

What's more, the country remains so fractured along sectarian and ethnic lines that it's doubtful whether any other politician could do a better job under Iraq's current system.

Such is the sobering reality facing the Bush administration three weeks before a watershed report to Congress on the state of Iraq after this year's U.S. troop buildup.

The White House can point to incremental progress at calming violence in Baghdad and other parts of the country. But the Bush administration cannot paper over the failure of al-Maliki's government to forge unity among the country's main groups: Shiites, Sunnis and Kurds.

Without some type of three-way accord, U.S. commanders warn that the recent military gains cannot be sustained.

Trying to read Bush's views on al-Maliki has become more complicated.

On Wednesday, he told a veterans' convention that the Iraqi leader is "a good man with a difficult job and I support him."

A day earlier, however, Bush caused a stir by acknowledging reservations about the Shiite prime minister's performance, citing "a certain level of frustration" with him.

"If the government ... doesn't respond to the demands of the people, they will replace the government," Bush said Tuesday. "That's up to the Iraqis to make that decision, not American politicians."

Meanwhile in Baghdad, U.S. Ambassador Ryan Crocker was telling reporters that political progress has been "extremely disappointing and frustrating to all concerned — to Iraqis, to the Iraqi leadership itself."

Sen. Carl Levin, chairman of the U.S. Senate Armed Services Committee, took the complaints even further, urging the Iraqi parliament to oust al-Maliki and replace him with someone less sectarian.

But that's unlikely to happen soon.

Ousting al-Maliki, a longtime Shiite political activist, would require a majority vote in the 275-member Iraqi parliament. As long as the Kurdish parties and the main Shiite bloc stand beside al-Maliki, his opponents lack the votes despite some recent defections by smaller parties.

Some of the remaining Shiite and Kurdish support for al-Maliki is based on fear of what might happen if he were to go. Under the constitution, the entire Cabinet would have to be dissolved, and all ministries would be up for grabs.

Deciding who would get the nearly 40 Cabinet-level posts could take months, paralyzing the government and perhaps jeopardizing recent security gains.

That is as unpalatable a prospect for U.S. policymakers as it is frightening for many Iraqis.

Al-Maliki himself is unlikely to give up without a fight. He told reporters Wednesday in Damascus, Syria, that he would "pay no attention" to his American critics and if necessary "find friends elsewhere."