Iraq's political leaders are showing promising new signs of progress toward reconciliation, yet still face difficult decisions on how to stabilize the country, Defense Secretary Robert Gates said Sunday.

"They seem to have become energized over the last few weeks," Gates told reporters who traveled with him from an international security conference in Munich, Germany. The Pentagon chief added that he wants to "see what the prospects are for further success in the next couple of months."

Gates arrived after dark at Baghdad International Airport aboard an Air Force C-17 cargo plane. He flew by helicopter to a private dinner with Iraq's political leaders, including Prime Minister Nouri al-Maliki, and the top U.S. commander in Iraq, Gen. David Petraeus, as well as U.S. Ambassador Ryan Crocker.

In an interview on the trip to Iraq, Gates cited the recent passage of an amnesty law as an example of political progress. He said he would ask Iraqi leaders to assess the prospects for other important steps such as passing a law that would spell out power-sharing between the provinces and the national government.

He likened the challenge of passing an Iraqi provincial powers law to the U.S. founding fathers' struggle to find a constitutional compromise on how to share power in the Congress between big and small states.

Gates said he would make clear to al-Maliki and other political leaders that "our continued eagerness for them to proceed and successfully conclude some of this legislation" considered key to reconciling Shiites, Sunnis and Kurds.

It was Gates' first visit this year and possibly his last before Petraeus and Crocker return to Washington in April to recommend to President Bush whether to continue reducing U.S. troop levels after Petraeus' current drawdown plan is completed in July. By then, four brigades are to have gone home, leaving 15.

"I would be interested in how they are planning it — which units are coming out" between now and July, Gates said.

The trickier question is whether Petraeus will tell Bush that security conditions in Baghdad and elsewhere in the country have improved enough to permit even more troop cuts without risking a deterioration in security. Petraeus' strategy is based on an expectation that improved security over time will give Iraqi political leaders an impetus to make compromises on legislation and other moves toward reconciliation.

Asked whether he would question Petraeus about the possibility of recommending a pause in the troop drawdown this summer, Gates replied, "I think our conversation will cover the whole range of possibilities."

He said on the way to Baghdad that he planned to visit troops Monday at a U.S. base in the capital, as well as pin a medal on Lt. Gen. Ray Odierno, the No. 2 U.S. commander. Odierno is departing after 15 months in charge of the headquarters that carries out Petraeus' strategy on a day-to-day basis.

Gates also was meeting with Odierno's successor, Lt. Gen. Lloyd Austin. Odierno is returning to Washington and has been nominated by Bush for promotion to four-star rank and assignment as Army vice chief of staff.

In his talks with Iraqi political leaders Gates said he intended to make clear "our continued eagerness for them to proceed and successfully conclude some of this legislation," which has taken longer than many had hoped.

Before his latest visit to Iraq, Gates said in a speech in Munich that NATO's survival was at stake in the debate over how the United States and Europe should share the burden of fighting Islamic extremism in Afghanistan.

As Gates cited signs of political progress, the U.S. military said a car bomb exploded near an Iraqi checkpoint in an open-market area north of Baghdad, killing at least 23 civilians and wounding 25. Earlier, the military said a diary and another document seized during U.S. raids show some al-Qaida in Iraq leaders fear the terrorist group is crumbling, with many fighters defecting to American-backed neighborhood groups.

Bush, in an interview broadcast Sunday in the United States, discussed the long-term U.S. relationship with Iraq. "We will be there at the invitation of the Iraqi government. ... We won't have permanent bases. I do believe it is in our interests and the interests of the Iraqi people that we do enter into an agreement on how we are going to conduct ourselves over the next years."

Last year, Bush ordered five additional Army brigades to Iraq. One of those brigades left in December and the other four are due to come out by July, leaving 15 brigades, or about 130,000 to 135,000 troops — the same number as before Bush sent the reinforcements.

Petraeus recently said it would be prudent to "let things settle a bit" before embarking on a new round of cuts. Gates has not said whether he agreed with Petraeus, though the secretary noted other commanders and service chiefs would weigh in with their opinions.

Bush, who met with Petraeus during his recent trip to the Middle East, said in the broadcast interview, "My message to the general was success is paramount and therefore, whatever you recommend, make it based upon the need to succeed."

"So we said, `What is succeed? What does succeed mean? It means there's enough security and stability for this reconciliation to continue to take place and for democracy to take hold," Bush said.

The president said he did not know what Petraeus or the Pentagon would recommend later this year on troop levels. "I will listen — give them careful consideration and make up my mind. But it's going to be based upon whether or not we can succeed or not."

At the German conference, Gates acknowledged that the U.S. has had innumerable disputes with its NATO allies in the 59 years since the security alliance was founded as a bulwark against the former Soviet Union. But Gates portrayed today's debate over the importance of the mission in Afghanistan and how to accomplish as among the most difficult ever.

A central theme was that Al Qaeda extremists, either in Afghanistan or elsewhere, pose a greater threat to Europe than many Europeans realize.

Gates said the Bush administration had learned from mistakes made in Iraq, including the need to more closely integrate the civilian-led stabilization efforts with the military efforts. He said the U.S. and NATO must apply that lesson in Afghanistan to assure success.