AMSTERDAM, Netherlands (AP) _ Mayors of some of the largest cities in the developing world said on Wednesday they are losing the fight against AIDS because of a lack of international support.

''This is the time for politicians around the world, the presidents, to come out and openly discuss AIDS,'' Mayor Daniel Kongo of Nairobi, Kenya, said at the eighth International Conference on AIDS.

''AIDS has thrown a great challenge in front of us, but we have limited resources,'' said Bombay's mayor, Chandrakant Handore.

Leaders of five urban centers in developing nations spoke in a special session at the conference. They included three - San Juan, Puerto Rico; Sao Paolo, Brazil; and Nairobi - whose AIDS infection rates are among the highest in the world.

San Juan Mayor Hector L. Acevedo conceded that the AIDS problem in his city was largely due to a reluctance of its citizens to accept the disease's deadly realities.

''In San Juan, we have two epidemics, the AIDS epidemic and the epidemic of denial,'' he said.

''We preach abstinence and monogamy, but 42 percent of our high school students, and 48 percent of our university students, have sexual relations in a very risky way.''