Admiral Timothy Keating said the USS Essex group will sail away from the former Burma on Thursday but leave several heavy-lift helicopters in neighbouring Thailand to assist in the relief effort.

"Should the Burmese rulers have a change of heart and request our full assistance for their suffering we are prepared to help," Keating, commander of U.S. forces in the Pacific, said in a statement.

Myanmar has been promised millions of dollars in aid from the United States, other governments and aid organisations.

But the junta has refused to allow the U.S. military to help distribute aid to affected areas, appearing due to fear that a large-scale international relief effort would loosen the grip the generals have held since a 1962 coup.

Thai Prime Minister Samak Sundaravej told visiting U.S. Defense Secretary Robert Gates in Bangkok on Sunday that the junta had rejected foreign military help in delivered cyclone aid because it feared it could be seen as an invasion.

Keating said they had made 15 attempts over the past three weeks to convince the regime to allow in U.S. helicopters and landing craft, "but they have refused us each and every time."

The United States had delivered more than 2 million lbs of relief supplies on 106 airlifts to Myanmar since the first U.S. military aid flight on May 12, Keating said.