BAGHDAD - The head of a Sunni-backed political bloc will join the Shiite-led government being assembled by his top rival, a spokeswoman said Tuesday, possibly ending months of tortuous, postelection dealmaking.

The breakthrough cements what the Obama administration has been pushing for as U.S. troops prepare to leave Iraq by the end of 2011: an inclusive government that distributes power among Shiites as well as the minority Sunnis and Kurds to forge stability after seven years of war.

Former Prime Minister Ayad Allawi, a Shiite with substantial Sunni backing, had held out for months, insisting he or one of his allies should be the next prime minister since his secular Iraqiya bloc narrowly won more seats than any other alliance in the March parliamentary election.

He had long said he would refuse to join a government led by Shiite Prime Minister Nouri al-Maliki, whom many Sunnis view with suspicion.

But after what appeared to be a warm 90-minute meeting between the two Tuesday, Iraqiya spokeswoman Maysoun al-Damlouji said Allawi agreed to join the government as head of a newly created council to oversee security and foreign-policy issues.

Allawi's turnabout essentially gives him veto power over many of Maliki's priorities. He will also earn the same salary as Maliki. The prime minister's current salary is believed to be $360,000 a year.

The détente came after intense lobbying by Vice President Biden. It was one of the last major hurdles Iraq's leaders wanted to clear before announcing the new government within a constitutionally required negotiation period that ends Dec. 25.

Aides said Maliki was now expected to announce the new cabinet Dec. 23. Parliament must then approve it.

Briefing reporters after the meeting, Allawi said strategic and national security affairs were the top topics, but he did not explicitly confirm he had accepted a post in Maliki's cabinet.

"We reached a joint vision," Allawi said. "Each of us has an experience that complements the other."

Maliki said the meeting focused on building a strong Iraq. "There are great challenges, and we have the ability to confront all these challenges," he said.

Damlouji said Allawi expected to have broad powers as head of the National Council for Strategic Policies, a 20-member body that will serve as a counterbalance to Maliki's major security and foreign-policy decisions.

Parliament is to meet Saturday to discuss the creation of the new council and its powers. A second aide to Allawi said 80 percent of the new council would have to approve the policies it oversees before they are enacted.

Last month, Allawi told CNN he would not join a Maliki government and described power-sharing efforts as dead. His comments came after Maliki cobbled together enough support from Shiite allies, including Iranian-influenced religious hard-liners, to remain as prime minister even though his own grouping fell short of finishing on top in the March 7 vote.

The election's failure to yield a clear winner threw Iraq into political chaos and stoked Sunni insurgents' hopes that they could use violence to return the country to the brink of civil war.

With a wary eye on the planned departure of American troops at the end of 2011, U.S. officials since have been pushing Iraqi leaders to broker a compromise.