PETROPAVLOVSK-KAMCHATSKY, Russia - U.S. and British planes carrying robotic undersea vehicles landed in Russia's Far East on Saturday to help rescue seven sailors trapped in a mini-submarine far below the Pacific Ocean.

The crew's limited oxygen supply was dwindling, but officials couldn't say exactly how much air remained. One official on Saturday said the supply could last another day.

The United States and Britain sent so-called Super Scorpios - robotic vessels that can investigate the accident site and possibly cut the sub loose from entanglements - at Russia's request.

The plea for international assistance underlined the deficiencies of Russia's once-mighty navy and strongly contrasted with the sinking of the nuclear submarine Kursk five years ago, when authorities held off asking for help until hope was nearly exhausted; all 118 crew members died in that accident.

But even with Moscow's quick call for help, rescue workers were racing to free the men before their oxygen supply ran out.

Navy officials have given various estimates of the air supply, with some saying it could last until Monday. Adm. Vladimir Pepelayev, deputy head of the navy's general staff, said on the NTV television channel Saturday that the air would likely last another day.

The cash-strapped Russian navy apparently has no rescue vehicles capable of operating at the depth where the sub is stranded. Its rescue efforts have focused on trying to grab and drag the sub with a trawling apparatus.

Pepelayev said underwater video cameras showed the submarine had been hooked, but the vessel was caught on an underwater antenna assembly that's part of Russia's coastal monitoring system. The antenna system is anchored with a weight of about 60 tons, news reports say.

Navy spokesman Capt. Igor Dygalo earlier told the Associated Press that rescuers had managed to move the sub about 60 yards toward shore by hooking onto a part of the underwater antenna the sub was caught on. A Russian remote vehicle that was transmitting pictures was helping to monitor the process.

Initial reports said the sub had become ensnared in a fishing net.

Dygalo said rescuers made contact with the sub crew at around 1:15 p.m. local time (8:15 p.m. Friday EDT) and their condition was reported to be "satisfactory." It wasn't clear how contact was being made or why it was only intermittent.

The events and the array of confusing and contradictory statements darkly echoed the sinking of the Kursk. That disaster shocked Russians and deeply embarrassed the country by demonstrating how the once-mighty navy had deteriorated as funding dried up following the 1991 Soviet collapse.

The new crisis underlined that promises by President Vladimir Putin to improve the navy's equipment have apparently had little effect. Authorities initially said a mini-sub would be sent to try to aid the stranded one, but the navy later said the vehicle wasn't equipped to go that deep.

Putin was sharply criticized for his slow response to the Kursk crisis and reluctance to accept foreign assistance. By midday Saturday, Putin had made no public comment on the latest sinking.

The airlifting of the American underwater vehicle to Kamchatka marks the first time since the World War II era that a U.S. military plane has been allowed to fly there. Since Soviet times, the peninsula has housed several major submarine bases and numerous other military facilities, and large areas of it are off-limits to outsiders.

The mini-submarine was trapped in Beryozovaya Bay, about 50 miles south of Petropavlovsk-Kamchatsky, the capital of the peninsula region north of Japan and west of Alaska's Aleutian Islands.

The vessel, which was participating in a combat training exercise, was too deep to allow the sailors to swim to the surface on their own or for divers to reach it, officials said.

After the Kursk disaster, Putin had called for serious improvements in the military's equipment and training, but little improvement has been noticed publicly. The navy reportedly ended its deep-sea diving training programs a decade ago due to funding shortages.

The trapped AS-28, which looks like a small submarine, was built in 1989. It is about 44 feet long and 19 feet high, and can dive to depths of 1,640 feet.