The UN statement said the last 45 pending visas had been granted to its

staffers, while Save the Children, Doctors Without Borders and the UN

Children's Fund have sent at least 14 workers into the delta in recent days.

 

The ruling military, apparently fearing that direct foreign participation in the aid operation could undermine its grip on the country, slapped a cordon around the hard-hit delta region for weeks.

 

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But while Myanmar's reclusive leadership appears to have acquiesced to UN pressure, it is continuing to stonewall offers of assistance from US warships deployed off the coast.

 

On Wednesday the top US military commander in the Asia-Pacific said that four US warships laden with relief supplies could the area within days unless its military government gives clearance for them to enter.

 

Admiral Timothy Keating, who heads the US Pacific Command, said he was frustrated Myanmar's government was not allowing the US navy to help.

 

Keating said he will make a recommendation to Robert Gates, the US defence secretary, "very soon" on what to do with the USS Essex and three other ships.

 

The Essex, an amphibious assault ship, has been off the coast of Myanmar for two weeks with a dozen helicopters, landing craft and marines that the US has offered to use to distribute relief to cyclone victims.

 

Wiped out

 

Myanmar's approval of pending aid worker visas comes after Ban Ki-moon, the UN's secretary-general, met with the head of the military government, Senior General Than Shwe, last weekend.

 

Since then, the regime appears to have kept its promise to allow humanitarian workers from all countries into the country and allow them access to the Irrawaddy delta.

 

There are still concerns about the true scale of the humanitarian disaster that Myanmar's government says has killed 78,000 people and left 56,000 missing.

 

Aid teams allowed into the disaster zone say they have found entire communities wiped out by the cyclone.

 

"The next humanitarian challenge will be getting the food, medicine, drinking water and shelter to the million or so people that haven't yet been reached," said Paul Risley, a spokesman for the World Food Programme office in Thailand.

 

Japan's foreign ministry said in Tokyo that the country sent a 23-member medical team to the country on Thursday.

 

Detention extended

 

While Myanmar's rulers have garnered some praise for opening up to international aid, global powers have voiced outrage at a government decision to extend the house arrest of pro-democracy leader Aung San Suu Kyi.

 

The Nobel Peace Prize winner has been held in jail or under house arrest for more than 12 of the past 18 years.

 

The extension of her detention came just days after representatives from 50 nations pledged up to $150m for the cyclone victims on Sunday.

 

"This measure testifies to the junta's absence of will to cooperate with the international community," Bernard Kouchner, France's foreign minister, said in a statement on Wednesday.

 

In Washington, George Bush, the US president, said on Tuesday he was "deeply troubled" by the decision, but stressed that the US would continue to provide aid to cyclone survivors.