YANGON, Myanmar - U.S. Navy ships laden with relief supplies will steam away from Myanmar's coast today, their helicopters barred by the ruling junta even though more than a million cyclone survivors still lack food, shelter and medical care.

"I am both saddened and frustrated to know that we have been in a position to help ease the suffering of hundreds of thousands of people and help mitigate further loss of life, but have been unable to do so because of the unrelenting position of the Burma military junta," said Adm. Timothy J. Keating, head of the U.S. Pacific Command.

The USS Essex and three other amphibious assault ships, which have been in international waters off Myanmar since May 13, will continue with their previously scheduled missions, Keating said in a statement issued by his headquarters in Hawaii.

But Keating added that "should the Burmese rulers have a change of heart and request our full assistance for their suffering people, we are prepared to help."

He said the United States had made "at least 15 attempts" to persuade the junta to allow the ships, which carry 22 medium and heavy helicopters, four landing craft, and 5,000 sailors and Marines, to deliver aid directly to victims in the most badly damaged areas.

The junta also refused help from French and British warships.

U.S. military transport planes are being allowed to fly in relief supplies to Yangon, the country's biggest city, from a temporary base in Thailand.

The Myanmar government says 78,000 people were killed by the May 2-3 cyclone and 56,000 are missing.

The junta, which explicitly rejected the use of foreign military helicopters in the relief effort, has also not authorized the entry of nine civilian helicopters flying on behalf of the U.N. World Food Program though they have been in Thailand since last week.

Only one helicopter chartered by the WFP was allowed in more than a week ago, and it did not begin flying supply missions from Yangon to the hard-hit Irrawaddy Delta until Monday.

Restrictions on travel by foreign workers, as well as on entry of some equipment, are hampering the aid effort, despite a pledge made almost two weeks ago by the junta's leader, Senior Gen. Than Shwe, to U.N. Secretary Ban Ki-moon to allow foreign aid workers free access to devastated areas.

"The small number of visas and the short duration of travel permits for access" into the delta area "continue to impose serious constraints on the effectiveness of overall operations," the International Federation of Red Cross and Red Crescent Societies said yesterday.

Despite the problems, the World Health Organization reported cause for optimism.

In a report circulated yesterday, it cited an assessment by the U.N. Children's Fund of conditions in hard-to-reach areas outside the town of Bogalay, one of the areas worst affected by the storm.

It quoted the assessment as saying that "there were no post-cyclone deaths in any of the villages assessed" as well as no signs of acute malnutrition. It also said suitable sources were found for clean water, assuming use of some form of treatment.