Storm blows out third Russian bid to save marooned sailors

But navy commander Admiral Vladimir Kuroyedov said he was more optimistic about the third try and that rescuers were still trying "actively" to join up with the huge submarine.

Meanwhile, with the crew thought to have just 48 hours of oxygen left, Russian navy officials were due to meet their NATO counterparts in Brussels on Wednesday to discuss Western help.

Navy officials said that at least two rescue capsules, capable of evacuating up to 20 people at a time, were involved in the latest attempt to rescue the crew launched at 0400 GMT.

"Up until now attempts to dock the rescue capsule with the Kursk submarine have failed," RIA quoted a navy spokesman as saying.

"He assessed the situation as difficult…and the operation was being hampered by bad storm conditions," it said. Kuroyedov said rescuers would not give up.

"The capsules will work until the result is achieved," Itar-Tass news agency quoted Kuroyedov as saying.

"Now I feel far more confidence that the operation to rescue the Kursk crew will produce a result," said the commander, who has so far adopted a bleak view of the rescue prospects.

The men, trapped in darkness on the damaged vessel which sank when they shut off the reactor after an accident at the weekend, were likely to be lying down to save energy as air runs low, a navy spokesman said.

Cooped up inside the vessel, they have tapped out signals heard by rescue teams, but these have become fainter.

The last time rescue vessels in the area monitored SOS signals tapped by the submarine crew was on Tuesday afternoon.

However the head of the Northern Fleet press office, Vladimir Navorotsky, was quoted as saying contact had not been lost.

Interfax

news agency quoted Kuroyedov as saying the crew had enough oxygen for two more days. "We will maintain optimism about the outcome of the operation until August 18," he said.

Kuroyedov said he was not surprised by the pause in tapping.

"One needs to take into account the mentality of submarine officers. Once they knew rescue capsules were above them, they maintained silence," he said, referring to the need for the sailors to avoid physical effort to save oxygen.

Kuroyedov has said that if attempts to evacuate the crew using capsules fail, two 400-tonne inflatable pontoons may be used to lift the whole vessel.

But Tass quoted the Northern Fleet press office as saying pontoons could not lift the huge sub to the surface. Rather, they could raise it from the seabed 108 metres down to a depth of some 50 metres (150 feet) where scuba divers could operate.

Russia has 22 ships on the surface involved in the rescue bid and has not yet accepted offers of Western help.

The daily newspaper Sevodnya quoted navy sources as saying Russian officers so far had rejected offers of help from the West for fear of being sacked.

"Admirals for some reason think that if even one Russian sailor is saved from a Russian submarine with outside help, it certainly will end in a political catastrophe," it quoted a source as saying.

Britain said on Wednesday it was preparing to fly out a submarine to help the rescue effort. A British Defence Ministry spokesman said: "We are getting ourselves ready so we can act immediately if the call does come through."

The spokesman said an LR5 mini-submarine was being loaded onto a plane at Prestwick airport in Scotland. The LR5 has a crew of three and is capable of rescuing 16 people at a time.