A filephoto taken in August, 2000 shows an AS-28 mini-sub (left), which is of the same model with the stranded Russian sub. -- Xinhua/AFP

Rescue vessels from the Russian Pacific Fleet have managed to catch an underwater object in their trawling nets, but it was unclear whether it is the trapped mini-submarine, a spokesman for the Pacific Fleet told the Interfax news agency.

"I would estimate the situation to be 51 percent in our favor,"the spokesman said.

"The cable is being strained now. If it is the mini-submarine, then it will be pulled up to a depth of 100 meters, so that divers could work on its body," he said.

The AS-28 mini-submarine got entangled with a fishnet Thursday night on the seabed off the Kamchatka Peninsula, about 200 km south of Kamchatka's regional capital Petropavlovsk-Kamchatsky. The submarine was at a depth of 190 meters, too far down to allow the crew to evacuate.

Russian Pacific Fleet Commander Admiral Viktor Fyodorov said a comprehensive operation to rescue the mini-submarine will start ina few hours time. Ten vessels, including two rescue ships and a sea towboat, are currently involved in the operation.

Reports on supplies aboard for the crew varied from one to three days worth of food, water and oxygen, but medical experts warned conditions on the vessel are worsening.

Fyodorov told Russia's Channel One television that the submarine had only enough air onboard to last "a bit more than 24 hours," but he was later quoted by Interfax as saying the vessel had enough air to last until Aug. 8.

Russia asked Japan, the United States and Britain to assist the rescue operation hours after the news of the accident broke out.

Japan's Defense Agency has dispatched four vessels of the Maritime Self-Defense Force to join the rescue efforts but it would take three to four days for the vessels to reach the accident site.

A US plane carrying 30 rescuers and two unmanned Super Scorpio deep diving submarines is set to leave San Diego, California, at 10:30 p.m. Moscow time (1830 GMT) and expected to arrive in Petropavlovsk-Kamchatsky at 7:00 a.m. Moscow time (0300 GMT) Saturday at the earliest, Interfax said.

Britain will airlift a Scorpio underwater rescue vehicle, capable of cutting iron covering or cables, Anton Atrashkin, spokesman for the British Embassy in Moscow, told Interfax.

"The equipment is being loaded onto a C-17 aircraft, which will soon leave Prestwick airport outside Glasgow for Petropavlovsk-Kamchatsky, where it is expected to arrive in about 11 hours time," Atrashkin said.