U.S. Defense Secretary Robert Gates, arriving in Iraq on an unannounced visit Thursday, said he plans to tell Iraqi leaders that the U.S. commitment for a military buildup in the country is not open-ended.

Speaking to reporters in Israel just before a quick flight to Baghdad, Gates said the ongoing debate in Washington about financing the military presence in Iraq has sent the message that both the U.S. government and the American public are running out patience with the war.

"I would like to see faster progress," he said, adding that momentum by the Iraqi government on political reconciliation as well as legislation on sharing oil revenue sharing would "begin the process to send a message that the leaders are beginning to work together."

He said that, in turn, would create an environment in which violence could begin to be reduced.

Underscoring a sense of urgency, police said a suicide car bomber rammed into a fuel truck in central Baghdad only hours before Gates' arrival, killing at least 11 people.

"It is every important they make every effort to get this done as soon as possible," he said, noting that an attack last week by a suicide bomber on a cafeteria at the Iraqi parliament inside the U.S.-guarded Green Zone made people particularly nervous.

He planned to meet in with Iraqi political leaders as well as U.S. military commanders.

The visit, his third to Iraq since taking over as defense secretary in December, came a day after U.S. President George W. Bush meet congressional leaders to discuss the impasse over legislation to provide funds for the war effort in Iraq and Afghanistan.

Gates said he has had no discussions with the White House about an absolute deadline by which the Pentagon must get additional funding to be able to maintain the mission.

During an hourlong meeting Wednesday at the White House, the president told lawmakers directly he will not sign any bill that includes a timetable for a troop withdrawal, and they made it clear Congress will send him one anyway.

"We believe he must search his soul, his conscience and find out what is the right thing for the American people," U.S. Senate Majority Leader Harry Reid told reporters after the session. "I believe signing this bill will do that."

But White House spokeswoman Dana Perino said, "It appears that they are determined to send a bill to the president that he won't accept. They fundamentally disagree."

Democrats hope to complete work on a House-Senate compromise in time to send it to the White House by the end of next week, with Bush's veto a certainty.

Given the narrow Democratic majority in the Senate, it appears unlikely the compromise will include a mandatory date for a complete withdrawal.

In any event, after an expected presidential veto attention would turn quickly to a new bill and how quickly it could be passed with provisions acceptable to the president.