Burma's military junta appeared to have backtracked today on a decision to give the US military permission to fly in relief supplies for the survivors of Cyclone Nargis and continued to block a major international effort to deliver emergency food aid.

More than 100,000 people are feared to have been killed in Saturday's cyclone and perhaps a million left homeless, but official and non-governmental relief workers have mostly been refused entry visas by the secretive South East Asian state.

Thai officials said today that they had brokered an agreement to allow US planes to break off from joint military exercises with Thailand to kickstart the relief effort.

"They were very suspicious that the Americans would do more than just distribute relief supplies, but we helped convince the Burmese to allow the Americans in," Boonsrang Niumpradit, Thailand's military chief, told Reuters.

The United States is still waiting for approval to start military aid flights for survivors, its ambassador to Bangkok said today.

"This morning, we and our Thai allies thought we had a decision from the Burmese leadership to let the C-130 in. As of now, we don’t have that decision," Eric John told a news conference in the Thai capital.

"We don’t have permission yet for the C-130 to go in but I emphasise ’yet', Mr John said.

Separately, the Foreign Office said that 17 Britons remain unaccounted in Burma following the storm that devastated the Irawaddy delta.

The British nationals – who were either visiting the country or live as residents there – have failed to make contact with friends or family in the UK five days after the disaster struck.

The Foreign Office stressed that problems with communications could be the reason, adding that they had heard no reports of any British casualties caught up in the emergency.

Despite growing international pressure – today China, a close ally of the Burmese regime, joined the call for Rangoon to open its doors – the UN's World Food Programme remains blocked.

Paul Risley, a WFP spokesman in Bangkok, said that three flights were waiting to leave Dubai, Bangladesh and Thailand with about 45 tonnes of high-energy biscuits, although a scheduled Thai Airways cargo flight did arrive with some of the biscuits.

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