The top U.S and British diplomats made a surprise trip to Iraq on Sunday to prod the country's struggling leaders to end nearly four months of wrangling and form a new government.

"We're going to urge that the negotiations be wrapped up," Secretary of State Condoleezza Rice said as she and British Foreign Secretary Jack Straw flew overnight to the Iraqi capital for meetings with the interim government and ethnic and religious power brokers.

Straw said the choice of leaders is up to Iraqis alone. But neither he nor Rice disguised the blunt nature of their mission.

"There is significant international concern about the time the formation of this government is taking, and therefore we believe and we will be urging the Iraqi leaders we see to press ahead more quickly," Straw said.

The British diplomat was making his third trip to Iraq this year. Rice was last in Iraq in November.

"We've wanted to be out there at times that we thought we could help move the process forward," Rice said. "And of course it's important to have fresh messages from time to time from Washington and from London about the concern that a government be formed."

Britain is Washington's closest ally in the 3-year-old war and stations the second largest number of troops in the country after the United States.

Rice and Straw were meeting with President Jalal Talabani, Vice President Adil Abdul-Mahdi, Prime Minister Ibrahim al-Jaafari and other leaders.

The diplomats' visit comes amid growing pressure on al-Jaafari to step aside as the Shiite nominee for a second term to break the stalemate in talks on forming a new government.

"We spoke about the Iraqi problem in general, about the government formation and the security problem," Sunni Arab politician Adnan al-Dulaimi said. "We also talked about hurrying up in forming the government because the Iraqi people have grown bored of waiting. Our points of view matched."

Asked if they discussed the nomination of al-Jaafari for prime minister, al-Dulaimi said only, "We discussed everything."

Before sitting down with al-Jaafari, Rice and Straw posed for pictures with stiff smiles. Rice looked especially uncomfortable, and said little before the cameras were ushered away.

She did not answer a reporter's question about whether she would tell the prime minister he is through.

A statement released by Talabani's office said he discussed "the efforts exerted by the representatives of the political blocs" with Rice and Straw.

Talabani also briefed his visitors on the negotiations and on the decision to form a political council for national security and a ministerial committee for national security, the statement said.

"The political will of the Iraqi leaders has not been shaken," Foreign Minister Hoshyar Zebari said Sunday.

"We are making some modest achievements, but everybody is on track, everybody's talking, everybody is compromising. The main problem is one of time. We are losing a great deal of time and unless this government is formed to be up and running, definitely, I believe, seriously, that there will be more killing and more Iraqi bloodshed," he told CNN's "Late Edition."

Talks among Shiite, Sunni and Kurdish leaders have stalled, in part because of opposition to al-Jaafari's nomination by the Shiite bloc. On Saturday, Shiite politician Qassim Dawoud joined Sunnis and Kurds in urging a new Shiite nominee, the first time a Shiite figure has issued such a public call.

"The prime minister can be a national hero by announcing his withdrawal so as to speed things up," Dawoud told The Associated Press on Sunday.

He raised the possibility that al-Jaafari's opponents within the Shiite alliance could name an alternative candidate if the prime minister did not withdraw soon.

A second Shiite legislator, Jalal Eddin al-Sagheer, echoed Dawoud's sentiments, saying Sunday that al-Jaafari no longer had the acceptance of Iraqi parties and foreign countries.

"There is no other way out of the government formation problem," said al-Sagheer, a member of the United Iraqi Alliance and of the Supreme Council for the Islamic Revolution in Iraq.

Rice, who was visiting Straw in northern England over the weekend, arrived with the British minister during a driving rain and thunderstorm. Their trip comes at a time when U.S. officials in Iraq have expressed increasing impatience with the slow pace of government talks following the Dec. 15 elections.

U.S. Ambassador Zalmay Khalilzad has urged the Iraqis to speed up the process to prevent the country from sliding into civil war.

U.S. officials believe the formation of a government of national unity would be a major step toward calming the insurgency and restoring order three years after the U.S.-led invasion toppled Saddam Hussein. That would enable the U.S. and its coalition partners to begin withdrawing troops.

But talks among Iraqi political leaders have bogged down, prompting Sunni Arab and Kurdish politicians to call for al-Jaafari's replacement. The Shiites get first crack at the prime minister's job because they are the largest bloc in parliament.