The United States said Wednesday it has begun contacts on a new U.N. Security Council resolution penalizing Sudan for non-cooperation on Darfur. The Bush administration is also planning its own sanctions after Sudanese President Omar al-Bashir, in a letter to the U.N. this week, appeared to renege on a new Darfur peacekeeping force. VOA's David Gollust reports from the State Department.

Officials here are disappointed by the al-Bashir letter, which they say leaves the international community with little choice but to seek new punitive measures against the Khartoum government.

The Sudanese leader last November embraced a plan for a "hybrid" peacekeeping force of some 21,000 African Union and United Nations troops to replace the financially-strapped, 7,000-member AU observer mission now deployed there.

Sudan has admitted a small contingent of logistics experts to lay groundwork for the new force. But in his letter to U.N. Secretary-General Ban Ki-moon this week, Mr. al-Bashir rolled back on his acceptance of 3,000 U.N. troops, police and helicopters to further prepare for the deployment.

A senior official here said the letter is a "pretty clear signal" that the U.N. can no longer expect Sudanese cooperation on the hybrid force.

State Department Deputy Spokesman Tom Casey told reporters U.S. and British diplomats have begun contacts on a new Security Council resolution to step up pressure on Khartoum.

He said, "We think it's important in light of the disappointing response that was received by the U.N. from President Bashir that the international community do consider what other steps would be appropriate."

"And this, frankly, is an issue that needs to come before the council, " he added.

Casey gave no indication of what a new resolution might contain or a time-frame for Security Council action.

But U.S. envoy for Sudan Andrew Natsios said the Bush administration is preparing its own parallel sanctions package.

In a conference call with non-governmental organizations, Natsios said the measures -- pending approval by President Bush - would include travel bans and asset freezes on key Sudanese officials, and curbs on dollar transactions by Sudanese companies.

Just back from a trip to the region including Sudan, Natsios said it is clear President Bush is angrier than anyone else in the administration about the peacekeeping delays, and continued Darfur violence outlined in a U.N. human rights report this week.

In a related development, the State Department urged Rwandan President Paul Kagame not to follow through on a threat this week to withdraw his country's troops from Darfur because of what he said is chaos in the region.

Spokesman Casey said Rwandan soldiers are critical to the mission, and said the United States wants other countries to step up and pledge troops for the thus-far undersubscribed hybrid force:

He said, "We very much appreciate what the Rwandans have been able and willing to do in Darfur. We certainly hope that presence will continue. And we think it's really time for some of the other countries in the region to step up as well."

Rwanda has some 2,000 troops in Darfur, about a third of the overall A.U. mission. It had been hoped that the new hybrid force would have been in place by January, but the process has been stalled by tactics of Sudanese government and the lack of troop pledges.