BALI, Indonesia — Defense Secretary Leon E. Panetta said on Sunday that despite hundreds of billions of dollars in expected cuts to the Pentagon budget, the United States would remain a Pacific power even as China expanded its military presence in the region.

Mr. Panetta, who is on his first trip to Asia as defense secretary, made the comments at a meeting of Southeast Asian nations on this Indonesian resort island. He sought to reassure Pacific nations that are concerned about China’s assertiveness that the United States, as he put it, would be “a force for peace and prosperity” here.

He acknowledged that nations in the region were worried about the impact of at least $450 billion in Pentagon budget cuts over the next decade and whether the United States could afford to maintain a strong military presence in the Pacific.

“There’s no question that those concerns have been expressed,” Mr. Panetta told reporters before meeting with the defense ministers of the 10 countries that make up the Association of Southeast Asian Nations. But, Mr. Panetta said, “I’ve made clear that even with the budget constraints that we are facing in the United States,” there is “no question that in discussions within the Pentagon, and discussions in the White House, that the Pacific will be a priority for the United States of America.”