The U.N. Security Council on Friday authorized a new peacekeeping mission with more than 5,600 troops for Burundi, adding to a series of U.N. operations that are taxing the resources of the international organization.

The new U.N. mission is designed to prepare elections for October 2005 in the French-speaking Central African country, where an 11-year civil war has cost more than 200,000 lives and forced more than 800,000 people from their homes. But it is adding to the burden on the United Nations as its peacekeeping is growing faster than at any time in more than a decade.

The United Nations, which oversaw a peacekeeping force of about 37,000 troops in 13 missions around the world in April 2003, is set to expand to an army of nearly 70,000 uniformed peacekeepers in 16 countries in the coming months. Most of those new peacekeepers will serve in French-speaking countries, including Burundi, Haiti and the Ivory Coast.

The new operations will cost an additional $1 billion by the end of the year, the United Nations estimates. The United States is required to pay more than 25 percent of U.N. peacekeeping costs.

Senior U.S. officials say that the new U.N. missions will contribute to U.S. efforts to restore peace in Haiti and in Burundi and other African trouble spots. But they acknowledge that they face a struggle in Congress to raise hundreds of millions in additional funds to finance them.

"Resources are stretched, both within our government and at the United Nations," Stuart Holliday, the U.S. representative for political affairs at the United Nations, said in an interview Friday. "The capacity issue will need to be addressed."

U.N. Secretary General Kofi Annan said that the U.N. missions are already being hampered by shortages of French-speaking peacekeepers, civilian administrators and a range of "specialized military capacities," including communications, logistics and advanced weaponry. "The scale of the current surge may well outstrip our capacities to backstop the operations," Annan told the Security Council last week.

With the world's most powerful armies committed to military operations in Iraq, Afghanistan and the Balkans, the United Nations has to rely on developing countries that frequently lack the capacity to equip their troops adequately or transport them to distant lands.

English-speaking peacekeepers from Pakistan, South Africa and Nepal will form the backbone of the peacekeeping mission in Burundi. But U.N. officials say they are engaged in an intense struggle with other U.N. missions to identify hundreds of qualified French-speaking police and civil administrators to serve in Burundi.

Despite the growing strains on the United Nations, Annan said he was pleased with the council's decision to establish the Burundi mission. "I hope the people of Burundi and the protagonists will see this as the interest the international community has in the process," he said. "It's gone on for too long and the people of Burundi have suffered enough."