The United Nations' two chief weapons inspectors will accept a new invitation by Baghdad to visit only if Iraq removes major obstacles now hampering inspections, the chief of the U.N. nuclear agency said Friday.

Mohamed ElBaradei said Iraq needed to allow inspectors to interview scientists in private and to use high-altitude surveillance planes.

"We need to make sure before we go that they are ready to move forward ... on these issues," ElBaradei said on arrival from New York in Vienna, headquarters of the International Atomic Energy Agency. "We will have first to see what they are offering before we decide on the visit."

ElBaradei spoke a day after Iraq issued an invitation to him and chief U.N. inspector Hans Blix to return to Baghdad for more talks before their next report to the U.N. Security Council on Feb. 14. The two head the U.N. inspection teams seeking evidence of hidden nuclear, chemical or biological weapons programs.

ElBaradei said he and Blix would be seeking meetings with the top leadership.

"It's very important that ... we meet at the highest level of the leadership, and hear from them a clear commitment that they are ready to be fully transparent," he told reporters.

While Blix and ElBaradei have met with senior officials heading Iraqi agencies dealing with the inspectors on their two previous trips, the nuclear chief's comments suggested he and Blix were seeking talks on a much higher level -- perhaps with Iraqi President Saddam Hussein himself.

The inspectors want to interview scientists privately in hopes of getting more information about Iraq's alleged weapons programs. Iraq says it has encouraged the scientists to comply, but so far none has agreed to talk to inspectors without an Iraqi official present.

President Bush has accused Saddam of threatening scientists with death if they agree to private interviews.

The invitation for another visit comes at a critical time, with the United States signaling increased impatience with the results of more than two months of U.N. inspections and maintaining the right to act militarily against Baghdad even without a U.N. resolution specifically authorizing it to do so.

Seeking to build support for the U.S. stance, Secretary of State Colin Powell plans to present evidence to the Security Council on Feb. 5.