WASHINGTON - Sen. Joseph R. Biden Jr., chairman of the Senate Foreign Relations Committee and a presidential candidate, called yesterday for the use of military force to end the suffering in Darfur.

"I would use American force now," the Delaware Democrat said at a hearing before his committee. "I think it's not only time not to take force off the table. I think it's time to put force on the table and use it."

In advocating the use of military force, Biden said senior U.S. military officials in Europe told him that 2,500 U.S. troops could "radically change the situation on the ground now."

"Let's stop the bleeding," Biden said. "I think it's a moral imperative."

Under U.N.-backed agreements approved last fall, a hybrid force of 22,000 African Union and U.N. peacekeepers is to be deployed in Darfur to protect and provide relief for 2.5 million Darfurians who have been forced from their homes and are now confined to camps.

"We must set a hard deadline for Khartoum to accept a hybrid U.N.-AU force," Biden said.

The Bush administration has always rejected use of military force in Darfur, partly because of a possible outcry, particularly in Muslim countries, about hostile U.S. action in yet another Islamic country after the invasions of Afghanistan and Iraq.

Andrew Natsios, the special U.S. envoy to Sudan, said the United States had agreed to a request by U.N. Secretary-General Ban Ki-moon for a two-to-four-week delay in imposing unilateral sanctions against Sudan so negotiations can occur on whether Sudan will accept international peacekeepers for Darfur.

Natsios said the United States was contemplating sanctions against 29 Sudanese companies, the same type of sanctions that have been imposed with some success on Iran and North Korea. If the sanctions are applied on the Sudanese companies, he said, they could hurt the country's economy.

Sudan's government has agreed to the initial stages of the proposed deployment. But President Omar al-Bashir has rejected full deployment, concerned that Sudanese sovereignty would be violated and the troops would arrest Sudanese officials suspected of authorizing war crimes.