President Bush telephoned President al-Bashir of Sudan to urge him to commit to reaching a peace accord with rebel groups in Darfur, as Deputy Secretary of State Robert Zoellick met with all sides in Nigeria in a bid to keep the talks alive.

White House Press Secretary Scott McClellan told reporters today that in the call, Mr. Bush told Mr. Bashir he sent Mr. Zoellick to foster a breakthrough, and asked the Sudanese leader to send his vice president, Ali Osman Mohamed Taha, back to the negotiations as a signal of Sudan’s desire to end the fighting.

“We will be looking for the government of Sudan to follow through on what the president brought up in the call,” Mr. McClellan said.

Mr.Taha walked away from the talks yesterday in Abuja, Nigeria’s capital, after a deadline imposed by the African Union and the U.N. Security Council passed with no agreement.

The human stakes in Darfur are high. Humanitarian organizations estimate that about 300,000 people have been killed and more than 2.4 million forced to flee their homes in fighting during the past three years. Tens of thousands are living in camps across the border in Chad.

A State Department spokesman, Sean McCormack, said Mr. Zoellick has already met with the American delegation to the peace talks; an African Union negotiator, Salim Salim, two rebel leaders and a representative of the Sudanese government.

“I can’t predict what the outcome is going to be, but as long as they are continuing to talk, that is good,” Mr. McCormack said. “They need to make the hard decisions for peace so that the killing can be stopped.”