Secretary General Kofi Annan asked the U.N. Security Council today to accelerate the hand-over of authority in East Timor from an Australian-led force to a U.N. peacekeeping mission, which could result in hundreds of millions of dollars in added costs for the United States.

Annan outlined the United Nations' plan to take control of all government functions in East Timor and rebuild the province as part of the most ambitious international attempt at reconstruction since the U.N. effort in Cambodia seven years ago.

The cost of the approximately 8,000 troops now patrolling East Timor is being paid by the countries that contributed them, with Australia bearing the largest burden and the United States a relatively small one. Annan asked for Security Council approval to replace that force with 8,950 U.N. peacekeepers funded according to the United Nations' standard formula, which requires the United States to pay 31 percent.

The United States already owes the organization about $1.7 billion in back dues and assessments for other peacekeeping missions. Congress has passed legislation cutting the U.S. share of U.N. peacekeeping costs from 31 percent to 25 percent, though that is a bone of contention with the world body.

The Security Council could vote on Annan's request as early as next week. Bernard Miyet, the United Nations' top peacekeeping official, said the new East Timor mission would probably be larger and more costly than the mission in Kosovo, which is expected to cost $500 million in its first year alone.

Many of the U.N. peacekeepers would be recruited from the Australian-led force now serving in East Timor, a former Portuguese colony that was seized by Indonesia in 1975 and voted overwhelmingly for independence on Aug. 30. The peacekeepers would remain until the Timorese develop the capacity to run their own affairs, a process that could take two to three years, U.N. officials say.

The hand-over underscores the growing price of new missions from Kosovo to Sierra Leone. Joseph Connor, head of the United Nations' department of management, said new peacekeeping missions could cost as much as $800 million over the next 12 months.

Annan, in an interview, declined to specify an amount but said "the figures will be substantial and the United States will be expected to pay. If they are going to give us these responsibilities, we need to have the resources."

The budget crunch presents the greatest challenge to Annan's ambition of creating a more activist world body able to halt internal conflicts and genocide around the globe. In a speech to a budget committee today, he noted that the United Nations has asked for an initial $200 million for the Kosovo operation and, so far, has received just $35 million in contributions.

It remains unclear whether Congress will agree to provide the U.S. share--either 31 percent or 25 percent--of the cost of a new mission for East Timor.

The Clinton administration and Sen. Jesse Helms (R-N.C.), chairman of the Senate Foreign Relations Committee, have indicated support for a U.N. role in the province. But there has been no substantive discussion of the price tag.

Richard C. Holbrooke, the U.S. representative to the United Nations, said today that Washington's willingness to pay its dues depends on the organization's ability to "achieve meaningful reform" and to cut the U.S. share of its costs.

"The United Nations needs to reduce its over-reliance on a single member," Holbrooke said. "A scale of assessments that is fair is not something the U.N. can just hope to do. It is what the U.N. must do."