U.S. officials are expressing optimism that peace efforts in Sudan will remain on track, despite the death of first vice president John Garang, and the ensuing violence in Khartoum and elsewhere. Two senior U.S. envoys begin talks in Sudan Wednesday.

Mr. Garang's death in a helicopter crash late Saturday triggered rioting in Khartoum and other parts of the country this week that has killed dozens of people.

But U.S. officials say the violence appears to have diminished from levels seen Monday, and they say they are encouraged by appeals for calm and efforts to restore order by both the Khartoum authorities and their new governing partners, the late Mr. Garang's Sudan People's Liberation Movement, the SPLM.

Mr. Garang, the southern rebel leader, became first vice president in a government of national unity that took office July 9 under the comprehensive north-south peace accord concluded earlier in the year.

Acting under terms of the accord, the SPLM has chosen Mr. Garang's longtime deputy Salva Kiir Mayardit to succeed him as head of the southern rebel movement and as first vice president in the unity government.

At a news briefing, acting State Department Spokesman Thomas Casey expressed satisfaction over the transition within the SPLM and urged an end to violence:

"We're continuing to look for, and what we are so far seeing, is an orderly and peaceful succession process for the position of first vice president, and that is something that's very positive," he said. "Obviously, we do continue to call on all Sudanese people to refrain from violence and to maintain calm, and continue on the path of non-violence and reconciliation, to continue to work together to fulfill Dr. Garang's legacy and to implement the comprehensive peace agreement."

The United States has devoted extensive diplomatic efforts to support the north-south peace accord and to reach peace in the Darfur conflict, and two senior State Department envoys have been sent to Sudan in the wake of Mr. Garang's death to try to keep peace efforts on track.

Assistant Secretary of State for African Affairs Constance Newman and the State Department's new special envoy for Sudan Roger Winter are due to have talks with Mr. Salva Kiir and other SPLM leaders Wednesday in the southern regional capital, Juba.

They will be in Khartoum Thursday for further talks including a likely meeting with Sudanese President Omar el-Bashir.

Deputy Secretary of State Robert Zoellick, who has been the administration's point-man for Sudan, is also involved in the diplomatic effort, speaking by telephone from Beijing with Mr. Salva Kiir.

He was also expected to speak with Sudanese Vice President Ali Osman Taha, who was representing Sudan at the funeral of Saudi Arabia's King Fahd.

A senior diplomat who spoke to reporters here said U.S. officials are pleased that leaders in Khartoum and in the SPLM have refrained from incitement and moved quickly to reaffirm their commitment to the peace accord.

He said one aim of the mission of Assistant Secretary Newman and Mr. Winter is to assure the parties that the death of Mr. Garang, who had close ties with Washington, does nothing to diminish the U.S. commitment to them, to moving forward with implementation of the peace plan, and to ending fighting in Darfur.

The comprehensive peace accord provides for wealth and power sharing by the Islamic authorities in Khartoum and the Christian and animist SPLM for six years leading to a referendum on the political future of the south. U.S. officials have said it could provide a model for a Darfur settlement.