The United States said Monday it is pressing Sudanese authorities to reconsider the apparent decision to expel country directors for two British aid agencies operating in the troubled western Darfur region.

The State Department says U.S. officials are very concerned by the reported move against the aid groups, which comes amid an upsurge in fighting between Sudanese government forces and rebels in Darfur.

The Sudanese expulsion notice came in letters to officials of the British charities Oxfam and Save the Children, which accused their country directors in Sudan of violating their status in the country by engaging in political activities.

Both aid groups have been prominent in relief efforts in Darfur, where more than a million and a half people have been displaced by fighting between government forces and their Arab militia allies on one hand and two local rebel groups on the other.

At a news briefing, State Department Spokesman Richard Boucher said the United States had joined United Nations officials in complaining about the expulsion move to Sudanese officials:

"These two non-governmental organizations have played, we think, an important role in helping alleviate the suffering of the people of Sudan, especially in Darfur," he said. "There are contacts at various levels of the United Nations operating in Sudan with Sudanese authorities to press the Sudan government to reverse these decisions, if indeed they have been taken. And that is something we will continue to press as well."

International relief groups have in recent weeks had to curtail some activities in Darfur amid a resurgence of violence in the nearly two-year-old conflict.

Spokesman Boucher said the United States joins the United Nations and the European Union in strongly condemning the violence and the failure of the Khartoum government to allow humanitarian assistance to reach the area.

But he said the latest escalation of violence was "instigated" by one of the rebel groups, the Sudan Liberation Movement and Army, and described the actions of the group as "illegal, inhumane, and clearly detrimental and counterproductive" for the Sudanese people.

The Sudanese government and rebels reached a cease-fire accord last April in Chad that was ostensibly reinforced by additional agreements earlier this month in the Nigerian capital, Abuja.

Mr. Boucher said the U.S. message to the rebel group is that if they want to engage the international community, they have to adhere to agreements they have signed.

The spokesman also said U.S. officials have expressed disappointment that Sudanese authorities have not been more responsive to repeated calls to take action against leaders of the "Janjaweed" militiamen, who have been blamed for widespread human rights violations in Darfur.

Mr. Boucher stressed the importance of continuing with the deployment of in Darfur of African Union truce monitors and troops protecting the observer mission.

He said the force, with airlift support from the United States, Australia and the Netherlands, currently numbers just over 800 members but should reach its authorized level of more than 33-hundred by early January.