FACTBOX- Iraq's security pact negotiations with U.S.

(Reuters) - Iraq and the United States are negotiating a security deal for U.S. troops to remain once a U.N. mandate expires at the end of the year.

The deal came under the spotlight last week when Iraqi Prime Minister Nuri al-Maliki raised the prospect of setting a timetable for the withdrawal of U.S. troops. Following are key facts about the talks:

WHAT IS BEING NEGOTIATED?

Talks were initially for a formal Status of Forces Agreement, similar to pacts Washington has with some 80 countries. Partly because of domestic pressure in Iraq, negotiators are now working on a temporary deal that Iraqi officials call a memorandum of understanding. A U.S. official close to the negotiations said this week it could be seen as a "bridging" document to last for perhaps 12-18 months once the U.N. mandate expires. Washington had set a goal of completing talks by the end of July, but this appears unlikely.

WHAT HAVE BEEN THE POINTS OF CONTENTION?

While White House officials have rejected setting a firm timetable for troop withdrawals, the U.S. official close to the negotiations said the deal would incorporate "goals" for the U.S. transition and that these "might include dates". Iraqi officials also use the more general term of "time horizon" for any troop departure.

Iraq has said that Washington had dropped a demand for immunity from prosecution for private contractors working for the U.S. government. The U.S. official declined to state Washington's position but when asked if it was unresolved said the issue would not be a "roadblock". Iraqi officials say planned U.S. military operations will be vetted by joint committees. The U.S. official said Washington supported the idea.

The detention of Iraqi prisoners is complicated, partly because 19,000 are still in U.S. custody in Iraq. The U.S. official said Iraq did not have the capacity to take them all but also did not want them all released.

Washington's security deals typically exempt U.S. troops from local law. The deputy speaker of Iraq's parliament has said lawmakers would likely veto any deal if U.S. troops had such immunity, something Washington is expected to insist on. The U.S. official said he believed the two sides could find "common ground" on the issue.