Bangkok, Thailand ? U.S. Navy ships are leaving Myanmar after failing to get the junta’s permission to unload aid to “ease the suffering of hundreds of thousands” of cyclone survivors, the top U.S. military commander in the Pacific said Tuesday.

Word of the aborted mercy mission comes even as the United Nations warned that a month after the cyclone swept through Myanmar, more than 1 million people still don’t have adequate food, water or shelter and junta policies are hindering relief efforts.

Adm. Timothy Keating ordered the vessels to leave the Myanmar area Thursday, after the U.S. made at least 15 attempts to convince Myanmar’s leaders to allow ships, helicopters and landing craft to offload their aid.

Myanmar’s state media has said that it feared a U.S. invasion aimed at seizing the country’s oil deposits. But the junta has also forbidden use of military helicopters from friendly neighboring nations, which are vital in rushing supplies to isolated survivors.

Keating, in a news release from Honolulu, said the USS Essex and accompanying ships would return if Myanmar’s leaders change their minds.

“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,” Keating said. Myanmar is also known as Burma.

U.S. Defense Secretary Robert Gates said Saturday that Myanmar’s obstruction of international efforts to help cyclone victims cost “tens of thousands of lives.”

Humanitarian groups say they continue to face hurdles from Myanmar’s military government in sending disaster experts and vital equipment into the country. As a result, only a trickle of aid is reaching the storm’s estimated 2.4 million survivors.