Baghdad ? Bowing to intense pressure, Prime Minister Ibrahim al-Jaafari agreed Thursday to allow Shiite lawmakers to find someone else to head the new government, abandoning his claim on another term in the face of Sunni and Kurdish opposition.

Al-Jaafari’s abrupt reversal was an apparent breakthrough in the monthslong struggle to form a national unity government. The Bush administration hopes such a government will curb Iraq’s slide toward anarchy and enable the U.S. to start bringing home its 133,000 troops.

Leaders in the seven-party Shiite alliance, the largest bloc in the 275-member parliament, were to meet today to begin choosing a replacement. But their field of candidates lacks stature and power, raising questions whether the new prime minister will be any more successful than al-Jaafari in confronting sectarian violence and the brutal insurgency.

It was unclear why al-Jaafari suddenly decided to relinquish the nomination that he won by a single vote with backing from radical anti-American cleric Muqtada al-Sadr during a ballot among Shiite lawmakers two months ago. Al-Jaafari had insisted Wednesday that stepping aside was “out of the question.”

But in a letter Thursday to the executive committee of the United Iraqi Alliance, the Shiite coalition, al-Jaafari wrote that he was prepared to “make any sacrifice to achieve” the organization’s goals. “I tell you, you chose me, and I return this choice to you to do as you see fit.”

Iraqi political parties agreed to postpone their scheduled parliament session until Saturday after Prime Minister Ibrahim al-Jaafari cleared the way for Shiite leaders to withdraw his nomination for a second term. From left, Iraqi Sunni politician Adnan al-Dulaimi, Parliament Speaker Adnan Pachachi and Iraqi President Jalal Talabani announced the postponement Thursday in Baghdad, Iraq.

“I cannot allow myself to be an obstacle, or appear to be an obstacle,” al-Jaafari said in an emotional address on national television. He said he agreed to a new vote so that his fellow Shiite lawmakers “can think with complete freedom and see what they wish to do.”

However, Kurdish politician Mahmoud Othman said al-Jaafari’s change of heart followed meetings Wednesday in the Shiite holy city of Najaf between U.N. envoy Ashraf Qazi and both al-Sadr and Grand Ayatollah Ali al-Sistani, the nation’s most prestigious Shiite cleric.

“There was a signal from Najaf,” Othman said. “Qazi’s meetings with (al-Sistani) and al-Sadr were the chief reason that untied the knot.”

Aides to al-Sistani, the spiritual leader of the Shiite alliance, said the ayatollah was frustrated about the deadlock in forming a government and alarmed by the rise in sectarian violence that followed the Feb. 22 bombing of a Shiite shrine in Samarra.

Many Shiite politicians had been quietly pressing al-Jaafari to step down but were reluctant to force him out for fear it would shatter the Shiite alliance and make the coalition appear weak.

Stepping up the pressure this month, Secretary of State Condoleezza Rice and British Foreign Secretary Jack Straw flew to Baghdad and demanded quick action to resolve the impasse. However, several Iraqi figures complained the U.S. and British intervention had prompted al-Jaafari’s supporters to dig in their heels against what many Iraqis considered foreign interference.

Shiite alliance leaders were to meet today to decide how to choose a nominee. If representatives of the seven alliance parties cannot reach a consensus on a single candidate, they will put several choices to a vote before the bloc’s 130 parliament members Saturday, officials said.

As the largest bloc in parliament with 130 seats, the Shiite alliance gets to name the prime minister subject to parliament approval.

But the Shiites lack the votes to guarantee their candidate’s approval unless they have the backing of the Sunnis and Kurds, whom they need as partners to govern.

Names most often mentioned as possible replacements include two members of al-Jaafari’s Dawa party, Ali al-Adeeb and Jawad al-Maliki. Neither is widely known among Iraqis, and neither has extensive experience in administration or government.