MONTEBELLO, Quebec (CNN) -- President Bush acknowledged a mood of "frustration" hanging over Iraq's fractious, paralyzed government Tuesday.
President Bush discusses Iraq's government at a news conference Tuesday in Montebello, Quebec.
But he stressed that it was up to Iraqis to replace their leadership.
Stymied by boycotts, bickering and bombings, the government of Prime Minister Nuri al-Maliki has been unable to take the political steps Iraqi and U.S. officials say are necessary to bring an end to the 4-year-old war.
The leaders of the U.S. Senate Armed Services Committee warned Monday that Iraqi leaders may be facing their "last chance" to hold the government together. The panel's chairman, Sen. Carl Levin called on Iraq's parliament to vote al-Maliki's "non-functioning" government out of office when it returns in two weeks.
Speaking at a news conference in Canada where he was meeting with the leaders of Canada and Mexico, Bush said Iraqi leaders had made some progress. But he said the government has "got to do more." Watch Bush describe Iraq's progress »
"The Iraqi people made a great step toward reconciliation when they passed the most modern constitution in the Middle East, and now their government's got to perform.
"And I think there's a certain level of frustration with the leadership in general, inability to work -- come together to get, for example, an oil revenue law passed or provincial elections," Bush said.
He said the "fundamental question" facing Iraqis is, "Will the government respond to the demands of the people?"
"If the government doesn't demand -- or respond to the demands of the people, they will replace the government," he said. "That's up to the Iraqis to make that decision, not American politicians."
Levin said al-Maliki's government was "too beholden to religious and sectarian leaders" to reach a political settlement of the country's sectarian and insurgent violence.
But government spokesman Ali Dabbagh criticized Levin's remarks, saying the Michigan Democrat had no right to criticize the Iraqi leader.
"The Iraqis will decide whether he will stay in the Cabinet or walk out," Dabbagh told CNN. "We do respect the Iraqis' final decision."
He added, "Being senator of the United States does not entitle him to talk about an elected prime minister in this way."
Earlier Tuesday, the U.S. ambassador to Iraq, Ryan Crocker, told reporters that progress toward reconciliation measures has been "extremely disappointing and frustrating to all concerned."
Crocker and Gen. David Petraeus, the top U.S. commander in Iraq, are to report to Congress next month on the political and military progress in Iraq.
But Crocker told reporters in Baghdad that it will take time for "meaningful reconciliation" to filter from the country's leadership to society at large.
"What has been happening in the last couple of years ... violence, population shift, displacement, tens of thousands of Iraqis killed. We are not just going to overcome that in a few weeks."
The government has been racked by walkouts during the current U.S.-led campaign to pacify Baghdad and its surrounding provinces -- a push aimed at buying time for al-Maliki and other Iraqi leaders to agree on plans to divide the country's oil wealth, hold provincial elections and allow former Baath Party members back into public life.
Cabinet ministers representing the movement of Shiite cleric Muqtada al-Sadr, and then members of Iraqi Accord Front, the Sunni bloc, left the government. Last week, two Shiite and two Kurdish parties signed an agreement forming an alliance, an effort spurred on by the embattled al-Maliki.
Those groups -- al-Maliki's Dawa party, the Shiite-led Supreme Islamic Council of Iraq, the Patriotic Union of Kurdistan, and the Kurdish Democratic Party -- are working to include a top Sunni party, the Iraqi Islamic Party, the major entity in the Accord Front. E-mail to a friend
CNN's Jomana Karadsheh contributed to this report.