Two miniature submarines yesterday morning prepared to descend more than 4km beneath the ice at the North Pole, according to Russian television.
The crew planned to drop a titanium capsule containing the nation's flag on the sea floor, symbolically claiming almost half of the polar region for Moscow.
In a feat mixing science, exploration and the scramble for potential oil and gas fields, the sub crews are attempting what Russian authorities called the first dive of its kind to the ocean floor at Earth's northernmost point.
The MIR subs and their three-member crews planned to plunge into the murky depths and spend several hours conducting the first close-up survey of the geologic structure of the seabed at the pole, according to Russia's Institute of the Arctic and Antarctic, which organized the expedition. The operation was expected to take eight hours.
The subs, two of only five manned submersibles in the world that can dive beyond 3km, are expected to return to the surface and their mammoth mother ship, the research vessel Akademik Fyodorov. One of the vehicles was featured in the 1997 movie Titanic.
Among those aboard the lead sub is Artur Chilingarov, a famed Soviet and Russian polar explorer. He became a hero of the Soviet Union in the 1980s, after leading an expedition aboard a research vessel trapped in Antarctic sea ice, and is currently a deputy speaker of the lower house of parliament.
"I'm not going to lie, of course it's dangerous," the 68-year-old Chilingarov said on Russian television, in video broadcast yesterday morning.
If recognized, the claim would give Russia control of more than 1.2 million square kilometers, representing almost half of the Arctic seabed.
Little is known about the ocean floor near the pole, but by some estimates it could contain vast oil and gas deposits.
The voyage has some scientific goals, including studies of the climate and biology of the polar region. But its chief aim appears to be to advance Russia's political and economic influence by strengthening its legal claims to the Arctic.
"I think that one of the tasks, at least for public consumption, is to put a claim and enlarge our territory by achieving the recognition of the Arctic shelf as a continuation of Russia's Eurasian part," Sergei Pryamikov, director of the international department of the St Petersburg-based institute, told Russia's RTR TV on Wednesday.