BAGHDAD - Making his third visit in four months to Iraq, Defense Secretary Robert Gates took a decidedly stronger tone as he warned the troubled nation's leaders that American patience is wearing thin.

US Defense Secretary Robert Gates arrives at Camp Falluja, Iraq, after visiting Baghdad, Thursday, April 19, 2007, and is greeted by soldiers and top military commanders. [AP]

On his unannounced trip, the Pentagon chief said Iraq's leaders have to move faster to bring together the warring factions.

Related readings:   Reid: US can't win the war in Iraq  Four blasts in Baghdad kill at least 183  PM: Govt not weakened by Sadr pullout  Al-Qaida-linked group making own rockets  Radical cleric's bloc quits Iraq Cabinet  Anti-US cleric threatens Iraq gov't  Grandmother blogs from Baghdad  Bombing at Iraqi parliament kills 8  US Army extends Iraq tours to 15 months

Gates had planned to take a look Friday at a key piece of the Bush administration's new anti-insurgency strategy, a joint US-Iraq security post where American and Iraqi forces live and work together to try to stop the violence that is ripping Baghdad. That tour, however, was abruptly canceled, and defense officials traveling with Gates said it was because his meeting with top US commanders went longer than anticipated.

Gates huddled in the former Al Faw Palace at Camp Victory for nearly three hours Friday morning with Joint Chiefs Chairman Gen. Peter Pace, the top Middle East commander, Adm. William Fallon, and Gen. David Petraeus and Lt. Gen. Ray Odierno, the No. 1 and 2 commanders in Iraq.

The session centered on operations in Iraq, as well as the progress of the ongoing military buildup, and it came as Gates ratcheted up the pressure on the Iraqi political leaders.

"The clock is ticking," Gates told reporters Thursday. "I know it's difficult, and clearly the attack on the council of representatives has made people nervous, but I think that it's very important that they bend every effort to getting this legislation done as quickly as possible."

A suicide bomber infiltrated the parliament building in the heavily fortified Green Zone a week ago, dealing a blow to the US-led effort to pacify the capital's streets.

Prime Minister Nouri al-Maliki called the violence in Baghdad an "open battle."

Since January, when President Bush announced his new strategy for the Iraq war - featuring a troop buildup and a renewed push for economic development and political progress - Gates and other senior administration officials have frequently and publicly reminded the Iraqis that they must act quickly to settle their differences.

They have attempted to strike a balance between pressuring the Iraqis to reconcile and reassuring them that the US military will not abandon them while they struggle to avert a full-scale civil war.

Gates said again Thursday that the Washington debate has been helpful in letting the Iraqis know that American patience with the war is ebbing. Democrats have seized on those remarks to bolster their arguments that there must be a deadline for the Pentagon to begin withdrawing troops from Iraq.

Speaking at a town hall-style gathering in Ohio on Thursday, Bush reiterated his opposition to any timetable for a troop withdrawal.

Gates said the Iraqis must, as quickly as possible, push through legislation on political reconciliation and the sharing of oil revenues among the Sunnis, Shiites and Kurds.