Russian rescuers focused on trying to loop cables under the antenna that has held the sub in a snare some 190 meters below the surface since Thursday.
Their aim was to lift both the antenna and the sub closer to the surface, where divers could reach the crew, a navy spokesman said on Saturday.
US and British crews escorting robotic undersea Super Scorpio vehicles landed on the rain-soaked Kamchatka Peninsula on Saturday and began to make their way toward the site about 15km off the coast.
Russian authorities hope the unmanned American and British submersibles, sent after a Russian plea for help, can cut the submarine loose. They are trying desperately to avoid losing a sub crew as they did with the Kursk nuclear submarine, which sank almost exactly five years ago, killing all 118 aboard.
A ship with British equipment left the port at Petropavlovsky-Kamchatsky in the middle of the night and was due to reach the site in Beryozovaya Bay on Sunday morning local time (Saturday night GMT).
The American submersibles and crews are expected hours later at the site off the east coast of Kamchatka, which juts into the sea north of Japan.
The Russian navy made contact with the crew late on Saturday, and Pacific Fleet commander Admiral Viktor Fyodorov said their condition was "satisfactory" despite temperatures of 5-7 Celsius, Fyodorov said.
"I assure you, work is continuing without interruption through night and day and will not stop until we actually lift our guys up to the surface"
Admiral Viktor Fyodorov,
Russia's Pacific fleet ommander
"They're not giving up hope," he said in televised comments.
"I assure you, work is continuing without interruption through night and day and will not stop until we actually lift our guys up to the surface," Fyodorov said.
It wasn't clear if contact with the crew was made by radio or through some other means; but officials said it was taking place every few hours.
Russia's plea for international assistance underlined the deficiencies of its once-mighty navy and strongly contrasted with the sinking of the Kursk in August 2000, when authorities held off asking for help until hope was nearly exhausted. Some of the 118 crew survived for many hours as breathable air ran out.
But now, even with Moscow's call for help, rescue workers are racing to reach the men in time.
Navy estimates of how long the air would last ranged from the end of Saturday until Monday.
Kursk sank almost five years ago,
killing all 118 aboard
Rear Admiral Vladimir Pepelyayev, deputy head of the navy's general staff, said the air would likely last to the end of the day and possibly through Sunday.
Fyodorov gave a similar estimate, but later was quoted by the Interfax news agency as saying there was enough to last until Monday.
Officials said the Russian submarine was participating in a combat training exercise and got caught on an underwater antenna assembly that is part of Russia's coastal monitoring system and is anchored with a weight of about 60 metric tonnes (66 short tonnes), according to news reports.