But Gates is not expecting fireworks at the meeting of American defense ministers in Bolivia, a U.S. official said, even though the group is working on an agreement to promote transparency in arms sales at a time when some are concerned about an arms race in Latin America.

"We're not expecting strong speeches," said the official, who spoke on condition of anonymity. "I think we're expecting a positive constructive dialogue like all the other conferences have been."

Gates travels to Chile on Friday for bilateral talks aimed at promoting deeper cooperation between the U.S. and Chilean militaries, especially on improving the military response to disasters like the 8.8 magnitude earthquake that hit Chile in February.

Gates flies to Bolivia on Sunday for the ninth Conference of the Defense Ministers of the Americas, a gathering that takes place every 18 months and is aimed at improving cooperation among the militaries.

The defense ministers will discuss issues like openness in defense budgeting, women in the military, disaster response and transparency in arms sales and purchases, the official said.