U.S. Secretary of State Colin Powell said Thursday, government-backed Arab militias in Sudan's western Darfur region have committed genocide against the local black African population. In Senate committee testimony, he urged international pressure on Khartoum authorities to rein in the militiamen and allow deployment of African Union monitors.

Mr. Powell's determination was based on an investigation by U.S. officials that included interviews of more than 1,100 Darfur refugees in Chad.

He told the Senate Foreign Relations Committee that genocide has been committed by the Janjaweed militias against the local population and it may still be occurring.

However, he said the finding would have no immediate effect on the Bush administration, which he said is already doing everything it can to try to curb the Darfur violence.

"So let us not be too preoccupied with this designation. These people are in desperate need and we must help them," he said. "Call it civil war, call it ethnic-cleansing, call it genocide, call it none of the above. The reality is the same. There are people in Darfur who desperately need the help of the international community."

Mr. Powell said he expects the Khartoum government to reject the State Department genocide finding, as it did a resolution drawing the same conclusion approved by both houses of the U.S. Congress in July.

He said there is a simple way for the Khartoum government to avoid the wholesale condemnation that comes with the genocide charges, and that is to "stop holding back, to stop dissembling" and end the militia attacks.

The secretary acknowledged there is, "no appetite" among western powers to assemble an intervention force to impose peace in Darfur.

But he praised the African Union's willingness to send in cease-fire monitors and accompanying protection forces, and said this could ratchet up pressure on Khartoum and increase the chances of bringing the situation under control.

Mr. Powell said the American-sponsored draft resolution now in the U.N. Security Council calls on Khartoum to cooperate fully with the expanded AU force, and raises the prospect of sanctions against Sudan's oil sector if it does not end the killing in Darfur.

Foreign Relations committee members were generally supportive of administration efforts, though Democrats including Wisconsin Senator Russell Feingold faulted the White House for not naming a special envoy for Sudan, when former Senator John Danforth vacated that role in June to become ambassador to the United Nations.

"This is no way to manage a crisis of this magnitude," Senator Feingold said. "Once again as I have for months, I strongly urge President Bush to appoint a senior envoy to focus exclusively on this crisis, each and every day to keep sustained pressure on Khartoum, and importantly to convince other key international actors to increase their engagement."

A State Department report that accompanied the Powell testimony cited a "consistent and widespread pattern" of atrocities committed by the Janjaweed against non-Arab villagers, often with military or air support by Sudanese government forces.

Mr. Powell called on the United Nations to formally investigate the violence under the 1948 U.N. Convention on Genocide, to which he noted Sudan is a party.