BANGKOK, Thailand — The head of the U.S. Pacific Command flew into Burma yesterday aboard the first U.S. military aid flight, to press for a full-scale international relief operation for victims of Cyclone Nargis. Facing mounting international pressure to open their country’s borders, Burma officials promised to consider the request.

In New York, U.N. Secretary-General Ban expressed “immense frustration” with the pace of the relief effort, slowed by Burma’s secretive military government. After trying for days to get top general Than Shwe on the telephone, Mr. Ban said, he sent a letter urging him to facilitate a giant aid operation.

Admiral Timothy Keating flew in a U.S. Air Force C-130 from an air base in Thailand that is turning into a staging area for relief for Burma. Accompanying him was the head of the U.S. Agency for International Development, Henrietta Fore. At the airport in Rangoon they conferred with Burma’s top naval officer in the highest-level military contact between the two countries in decades.

Admiral Keating and Ms. Fore did not go beyond the airport before flying back to Thailand. Ms. Fore said she believed that “our discussions were a good first step” toward broader American help.

America has offered to deploy as many as 4,000 Marines, six C-130 cargo planes, and a large number of heavy-lift helicopters in what would be its largest disaster relief effort since the Indian Ocean tsunami of 2004. It will also have three naval ships, with helicopters on board, positioned off Burma’s southwest coast within 48 hours.

“We have a broad array of personnel and equipment, and we are ready to respond as soon as the Burmese give us permission,” Admiral Keating said.

The cargo plane on which Admiral Keating and Ms. Fore traveled delivered bottled water, blankets and mosquito nets. American and Burmese military personnel jointly unloaded the supplies, which Burma officials promised to send quickly to the disaster zone.

Burma authorities cleared two more American C-130 relief flights for today. In another sign of gradual cooperation, U.N. officials said that Burma had now approved visas for 34 aid workers.

The American government, meanwhile, moved yesterday to allow individuals to send unlimited amounts of money to people in Burma. The generals who rule the country are highly wary of Western governments, especially America. President Bush has called Burma “an outpost of tyranny”; the generals accuse Washington of trying to overthrow them by supporting Burma dissidents, both in and outside the country.