U.S. officials expect Afghan President Hamid Karzai to concede on Tuesday that he fell short of the 50 percent vote share in August's election that he needed to win outright, but it was unclear Monday whether that would lead quickly to a runoff election with his nearest challenger, a U.S. government official said.

Karzai could opt to embrace a runoff, which Secretary of State Hillary Rodham Clinton said Monday was logistically feasible within weeks, or he could attempt to negotiate a power-sharing arrangement with former Foreign Minister Abdullah Abdullah, who finished second in the August balloting.

The U.S. government official, who discussed the matter on condition of anonymity because Karzai had not yet announced his decision, said it was not clear Monday which of the two avenues to settling the political crisis Karzai would pursue.

The U.S. preference is for a power-sharing deal to avoid the expense and risk of a second election.

Clinton said that Karzai intends to announce Tuesday how he will "set the stage" for resolving the country's postelection political stalemate.

"He is going to announce his intentions," Clinton told reporters at the State Department after meeting with Iraqi Prime Minister Nouri al-Maliki. "I am going to let him do that, but I am encouraged at the direction the situation is moving."

Clinton declined to say whether Karzai has decided to accept the findings of a U.N.-backed fraud investigation that threw out nearly a third of Karzai's ballots from the disputed August election and set the stage for a possible runoff.

Zalmay Khalilzad, who was U.S. ambassador to Kabul from 2003 to 2005 and who is in Kabul in a private role seeking to resolve the political standoff, said Monday that a power-sharing arrangement may be the best solution. He said he thinks that both Karzai and Abdullah are willing to work out a unity government.

"There is every indication that the Obama administration favors a unity government rather than another vote," Khalilzad said in an interview with ABC News. He added that such an arrangement could be problematic.

"I think the most likely outcome is a unity government, but a government that will take a long time to put together, may not be very strong and will not be necessarily a very effective partner given the internal disagreements within that government," he said.

Clinton did not address the prospect of a coalition, or unity, government headed by Karzai and Abdullah.

"I am very hopeful that we will see a resolution in line with the constitutional order in the next several days," Clinton said. "But I don't want to pre-empt in any way President Karzai's statement, which will set the stage for how we go forward in the next stage of this."

Clinton said she has spoken a number of times to Karzai in recent days.

Defense Secretary Robert Gates, meanwhile, said the Obama administration needs to decide on a war strategy and not "sit on our hands" waiting for election results and a government to emerge in Kabul. In remarks to reporters traveling with him to Asia, the Pentagon chief said President Barack Obama will have to make his decisions in the context of "evolving" issues.

At U.N. headquarters in New York, a spokeswoman for U.N. Secretary-General Ban Ki-moon said Karzai assured the U.N. chief that he will "fully respect" the constitutional process even if it means a runoff election.

The spokeswoman, Michele Montas, said Ban spoke with Karzai on Monday morning. Continued...