A senior US diplomat said today his country would have to find an alternative way to get aid in to cyclone-hit Burma if its secretive military rulers refuse help from Washington.

The comments by Scot Marciel, the newly appointed US ambassador to the Association of Southeast Asian Nations (Asean), came as dozens of relief workers are stranded abroad awaiting permission to enter the reclusive country.

Burma was hit by tropical cyclone Nargis over the weekend, killing at least 22,000 people and leaving 41,000 missing.

"We would hope they would accept assistance from the United States, it is meant sincerely from the American people," Marciel told reporters at the end of a two-day introductory visit to Malaysia, which like Burma is an Asean member.

"If not we would want to work with the UN and other organisations who are able to get inside the country," he added.

"Right now the focus needs to be on getting the assistance to the people."

Burma's rulers say they have appointed a minister to review visa applications by aid workers seeking to join the cyclone relief effort, but UN officials say no new visas have been issued.

The United States, which has for years pushed to tighten the sanctions that critics say have worsened the situation for Burma's people, said earlier it had ships nearby loaded with supplies.

"Let the United States come to help you," US President George W Bush said.

Controversial referendum to go ahead

But Burma's rulers are wary of the outside world - especially the United States, which has taken a hard line on the military regime.

Marciel said he was also surprised by the decision of the army rulers - in power since 1962 - to proceed with a constitutional referendum in most the country this weekend.

"It's a huge crisis and it just seems odd to me that a government would go ahead with a referendum in those circumstances," he added.

He blasted the referendum - intended to pave the way for multiparty elections - as "neither free, fair nor credible...," saying the constitution was drafted in secret with no open debate.

"We don't think that the referendum will contribute to national unity and help Burma move in the direction that I think everybody wants it to move," he said, referring to Burma by its former name.

Earlier this week, Burma's generals defied calls to postpone the referendum saying it would proceed except in the areas hardest hit by the cyclone.

The opposition party of democracy activist Aung San Suu Kyi, who has been detained by the junta for most of the past two decades, called that decision unacceptable.