UTAPAO AIR BASE, Thailand— With 11,000 troops, a flotilla of Navy ships and Air Force cargo planes converging on cyclone-devastated Myanmar, the U.S. military is readying its biggest relief operation since the tsunami of 2004.

It even has a name — "Caring Relief."

But as the first U.S. military plane arrived in Yangon with much-needed supplies on Monday — and as hundreds of thousands of refugees in Myanmar struggled to find food and shelter — just how far the military would be allowed to go remained a big question mark.

Adm. Timothy J. Keating, head of the U.S. Pacific Command, said Myanmar had not given permission for a full-scale U.S. relief operation Monday but added that authorities were "taking it under consideration."

In a major breakthrough, a gray C-130 cargo aircraft filled to the brim with 28,000 pounds of mosquito nets, blankets and water was unloaded in Yangon, Myanmar's largest city, providing what officials said was enough aid to help some 30,000 victims of the disaster.

The flight — repeatedly delayed by the reluctance of Myanmar's hermetic rulers, who are resistant to what they see as outside interference — was the first of what U.S. military officials hoped would be a steady flow of aid.

Two more flights were planned for Tuesday.

"We hope they will allow us to do more in the future. It's really just up to what the Burmese will allow us to do," said Lt. Col. Douglas Powell, the U.S. Marines spokesman for the operation.

Also aboard the flight was Keating, one of the highest U.S. military officers to visit Myanmar — also known as Burma — in recent memory.

After returning to Thailand, he told a press conference that U.S. Marines, six C-130s and a large number of helicopters were "ready to go forward as soon as the Burmese give us permission."

He said three U.S. Navy vessels would be positioned along Myanmar's southwest coat within 36 to 48 hours.

Keating said he would push hard for permission to ratchet up the military's involvement in the relief effort.

"We just want to help," Keating said before he boarded the flight at this air base in southern Thailand.

The U.S. ambassador to Thailand, Eric John, was more direct.

"The U.S. remains deeply concerned about the plight of the Burmese people," he said. "It is important that we, and the international community, be allowed to help.

"Let them in. Let them save lives," he said.

Even as they awaited the go signal, the military was preparing a massive relief operation, which it dubbed Joint Task Force Caring Relief.

Keating said the U.S. military could send in as much as 200,000 pounds of aid each day — nearly 10 times the amount that was on the first plane.

"We can bring anything that can be put in the back of a C-130," he said.

He said helicopters and naval assets could provide a huge boost to international organizations and non-governmental aid groups in need of transportation and support.

The troops were a major factor after the deadly tsunami that hit the area in 2004 and helped with relief efforts after cyclone Sidr hit Bangladesh last year.

"We have significant experience in the Pacific in times like this," Keating said.

The troops are already in place.

More than 11,000 troops are in Thailand for the annual Cobra Gold exercises along with four naval ships led by the USS Essex, which is like a mini aircraft carrier with helicopters on board and the capability to launch amphibious landings in hard-to-reach places.

More ships — including two aircraft carrier battle groups — could reach the area quickly but are for the time being hovering back in international waters. Their inclusion would vastly improve the logistics of any relief effort.

Officials have said that no aid will be flown in without the Myanmar government's permission, however.

Monday's flight was filled with humanitarian aid that was provided by a governmental agency, not the military itself, and Keating stressed that the flight was unarmed.

Myanmar state television announced Sunday the death toll from Cyclone Nargis had jumped by about 5,000 to 28,458, with another 33,416 still missing.

International aid groups say they fear the number could reach 100,000, and the British group Oxfam said up to 15 times that number could face death from a public health catastrophe if people do not get clean water and sanitation soon.