The U.N. Security Council agreed today on Hans Blix, a Swedish arms control expert, as the chairman of a new disarmament agency for Iraq, but diplomats cautioned that it remains uncertain whether Baghdad will allow the inspectors to return.

So far, Iraq has said it will not agree to a resumption of U.N. inspections, and key Security Council members remain divided over a range of core issues, from the recruitment of personnel for the new agency to procedures for handling and assessing foreign intelligence about Iraqi weapons programs.

U.N. officials said that Blix, director general of the International Atomic Energy Agency from 1981 to 1997, is not expected to begin work for a month. His initial task will be to establish an advisory board, called the College of Commissioners, and to organize the new agency, known as the U.N. Monitoring, Verification and Inspection Commission, or UNMOVIC.

The United States wants the new chairman to hire arms experts from the ranks of the U.N. Special Commission, or UNSCOM, the former arms agency whose members were withdrawn from Iraq a year ago, on the eve of U.S. and British airstrikes.

U.S. officials contend that UNSCOM's experts have a greater understanding of Iraq's secret missile and biological and chemical weapons programs than anyone outside the Iraqi military.

But UNSCOM also was discredited in the eyes of many diplomats by revelations that some of its members secretly gathered intelligence on Iraq for the United States. To establish a clean break, Russia, France and China want to create the new agency from scratch, including all new personnel.

"I don't expect any of the top UNSCOM experts will ever be able to go back to Iraq," said one diplomat who shares this position. "We need a new chairman, a new commissioner and new arms experts."

The United States and Britain intend to continue to provide the new agency with classified intelligence on Iraq's weapons activities, according to diplomats. But France hopes to persuade the new chairman to place limits on the new commission's ability to act on that intelligence.

A diplomat familiar with the French position said Paris would like Blix to establish an assessment team within the new agency to determine the credibility of foreign intelligence reports, so that UNMOVIC is not manipulated by any foreign power.

In the face of these disagreements, the selection of Blix was an unusual show of unity by the Security Council.

"Let those who saw divisions in the international community note that I am speaking now on behalf of a united council," said U.S. Ambassador Richard C. Holbrooke. "China was there. Russia was there. France was there."

Holbrooke noted Blix's support in Washington. "Everybody believes that he is extremely well qualified," he said.

U.N. Secretary General Kofi Annan today phoned Blix in Antarctica, where he is vacationing, and announced that the Swedish diplomat is willing to take the job.

"I hope that Iraq will cooperate," Annan said. "We are going to do everything we can to get them engaged in the game."