WASHINGTON, Oct 22 (Reuters) - The United States pressured the Iraqi government on Wednesday either to accept an agreement allowing U.S. forces to stay in the country beyond this year or to spell out its objections.

Comments from the White House, the State Department and the Pentagon appeared to show frustration at Iraqi criticism of a deal hammered out by U.S. and Iraqi negotiators on a new legal framework for the U.S. presence in Iraq.

Iraq has effectively asked to reopen talks on the status of forces draft that would require U.S. troops to leave by 2011 unless Baghdad asks them to stay and would allow Iraqi courts to try U.S. troops accused of serious crimes while off duty.

The United States, which invaded Iraq in March 2003 to overthrow former dictator Saddam Hussein, now has 155,000 troops in Iraq operating under a United Nations Security Council mandate that expires on Dec. 31.

"We're running out of time," said State Department spokesman Robert Wood. "The door is closing and ... it's time for the Iraqis to step up to the plate and make a decision."

Iraqi government spokesman Ali al-Dabbagh on Tuesday said Iraq's cabinet had decided to seek changes to the draft pact.

Separately, Iraqi Foreign Minister Hoshiyar Zebari said on Wednesday that Baghdad may seek changes to the wording of the draft pact but would not seek to renegotiate its "backbone."

Wood and other U.S. officials said the Iraqi government had not formally notified Washington of its objections and they could not address them until it did.

Asked what were the Iraqi objections, Pentagon spokesman Geoff Morrell told reporters: "I don't think we know."

U.S. Defense Secretary Robert Gates on Tuesday said "there is great reluctance to engage further in the drafting process" and said the door to changing it was "pretty far closed."

However, U.S. officials acknowledged it was possible that they could make some changes.

White House spokeswoman Dana Perino said U.S. negotiators would study any amendments the Iraqi government might propose but said there would be "a very high bar" to accepting them.

In one bald sign of U.S. frustration, a State Department official who asked not to be named said U.S. forces would have to stop providing personal protection to senior Iraqi officials if the U.N. mandate expires without a bilateral pact in place. (Additional reporting by David Morgan, editing by Jackie Frank)

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