The United States has made a high-level appeal to Sudan to halt any help it may be giving to rebels menacing the Chadian capital, N'Djamena. Remaining U.S. diplomats in Chad have left the embassy for the safety of the French-protected international airport. VOA's David Gollust reports from the State Department.

Bush administration officials are discounting Sudanese denials of involvement in the rebel offensive, and are calling on the Khartoum government to do all it can to curb the rebels and end the Chad fighting, which has added to the instability of the region.

Sudan has long been accused of sheltering and providing arms to the rebels and Chadian authorities alleged Sunday that Sudanese forces had provided air support for rebel attacks on government positions.

At a news briefing, State Department spokesman Sean McCormack said the United States has expressed its concern over the situation to the highest levels of the Sudanese government:

"We have gone in at very high levels of the Sudanese government to say that if there is any support from the Sudanese government to these rebels that that should end immediately, and that any influence they might have with the rebels they should use in order to tell them to withdraw," said Sean McCormack. "We've done this at the highest level of our embassy in Khartoum directly into the presidency as well as the ministry of foreign affairs."

In a statement Saturday, the State Department joined the African Union in condemning what it said was an attempt by rebels, entering from outside the country, to seize power in Chad. It appealed for calm and an immediate end to armed attacks.

Spokesman McCormack confirmed that the U.S. diplomatic staff in N'Djamena abandoned the embassy compound amid gunfire over the weekend in the city center.

Non-essential members of the U.S. embassy staff, along with the families all U.S. officials based in Chad, have been evacuated.

Only four U.S. diplomats, including Ambassador Louis Nigro, remain on duty - based temporarily at the N'Djamena international airport, which is being protected by French troops.

The evacuation of the embassy in Chad was the first incident of its kind in many years, perhaps since 1979 when Iranian militants took over the U.S. embassy in Tehran after Iran's Islamic revolution.

McCormack said the premises in N'Djamena were secured according to emergency procedures, which presumably include the destruction of classified documents and equipment.

The spokesman said the embassy compound remains sovereign U.S. territory under international law and said if rebels or others have entered the buildings, they should leave immediately.

The State Department Saturday warned Americans to defer non-essential travel to Chad because of the security situation, and urged those already there to consider departing.

McCormack said several hundred private U.S. citizens are believed to be in Chad, and that about 100 had availed themselves of evacuation flights in the last few days.