The unprecedented expedition is part of Russia's efforts to assert territorial claims well north of its Arctic coast in territory thought to contain significant oil, gas and other reserves.

"The Arctic is ours and we should demonstrate our presence," the expedition's 67-year-old leader, the explorer and member of parliament Artur Chilingarov, said on television earlier.

Chilingarov, fellow parliamentarian Vladimir Gruzdev and scientist Anatoly Sagalevich aim to descend in the Mir submersible vehicle 4,200 metres (14,000 feet) to the bottom of the Arctic Ocean beneath the pole.

Organisers even have a tentative plan for a telephone link-up with the International Space Station from the seabed.

On Thursday the nuclear-powered ice-breaker Rossiya, designed to cut through heavy ice at speed, set off for the pole from the Barents Sea port of Murmansk.

It was to be followed just after midnight by the expedition's "flagship," the Akademik Fyodorov, expedition organiser Vladimir Strugatsky told AFP.

Once on the seabed the three men on board the Mir will carry out scientific experiments and probes and will leave behind a Russian flag and a capsule containing a message for future generations, Sagalevich said in an interview with the Izvestia newspaper.

The descent is expected to begin on Sunday.

The expedition comes amid heightened international interest in the Arctic, prompted by increased melting of the ice as well as expectations of untapped energy reserves.

Earlier Chilingarov said the expedition would help advance Russia's Arctic claims, which are disputed by other countries, including the United States.

In 2001 Russia made a submission to a United Nations commission claiming extra territorial waters off its northern coast.

The claim is based on the contention that a ridge of seabed known as the Lomonosov Ridge, which extends into northern Canada, is actually an extension of continental Russia.

The United States has opposed Russian attempts to claim absolute control in large swathes of ocean off its northern coast, arguing that these waters should from a legal viewpoint be fully open to international shipping.

In a statement, Gruzdev said: "We must remind the whole world that Russia is a great polar and scientific power."

In Tuesday's Izvestia interview Sagalevich described the difficulties he expected to encounter, particularly when returning to the surface.

"The ice ceiling above our heads will be of varying thickness, from a metre to dozens of metres. With the help of our navigational equipment we will have to find a big enough gap," he said.

In a speech aboard a nuclear ice-breaker in May, President Vladimir Putin called for greater efforts to secure Russia's "strategic, economic, scientific and defence interests" in the Arctic.

The polar expedition has been portrayed by media here as an epic quest reminiscent of past eras of polar discovery.

"The coming event is considered historic, both in terms of the unique sub-sea descent and even more importantly in terms of Russia's strategic interests in the Arctic," the weekly newspaper Russky Kuryer said.

Russia's 2001 submission to the Commission on the Limits of the Continental Shelf has yet to be ruled upon.

Another twin project of Chilingarov's is to develop the maritime passage that runs across the top of Russia between Europe and Asia known as the Northern Sea Route. The route could potentially cut thousands of kilometres (miles) off shipping routes between Europe and Asia.