A Russian ship carrying vital fuel supplies is battling through thick ice to reach parts of frigid Alaska cut off by a severe winter storm in the US state, officials said Wednesday.

Helped by a US Coast Guard ice-breaker, the Russian tanker "Renda" is less than 100 miles (160 kilometers) away from the port town of Nome on Alaska's remote western coast, across the Bering sea from Russia's far east.

It is the first time such a fuel delivery has been attempted through some 300 miles of ice in the depths of winter, after bad weather in the fall stopped supplies reaching Nome before the heavy ice and snow began.

By Wednesday the "Renda" and the US cutter "Healy" were some 95 miles south of Nome, said Coast Guard spokeswoman Veronica Colbath.

But wind and currents were making progress difficult, while the "Renda" was having to be rescued itself by the "Healy" when ice built up quickly around the Russian vessel, despite it following in the wake of the ice-breaker.

"They have been experiencing a lot of weather challenges with the wind and the currents, that have made it difficult for them to make a lot of progress," she told AFP, saying ice was up to four feet thick in places.

The bone-chilling weather is harsh even by Alaska's standards, with huge snowdrifts and temperatures plunging down to 35 below zero Celsius (minus 31 Fahrenheit), according to the National Weather Service data.

The Coast Guard spokeswoman said temperatures had been down to minus 50 degrees on the two boats, which have already battled together through some 200 miles of pack ice.

The Russian ship is carrying 1.3 million gallons of fuel for Nome, a city of some 3,500 people which did not get its usual pre-winter oil delivery due to a storm in the fall.

A special waiver had to be granted to allow the "Renda" to head to the rescue, as normally only US-owned and operated vessels would be allowed to make such deliveries, under a 1920 US law.

The Coast Guard spokeswoman said the ice conditions are well within the capabilities of the US vessel.

"But... the 'Renda' has gotten stuck, because of the pressure on the ice, which has closed in pretty quickly around the 'Renda' and then the 'Healy' will have to go back round and ... help the 'Renda' proceed forward," she said.

The ship was originally due to dock in Nome on Monday this week, but the latest estimate is that the ship is not expected to arrive until Friday, at the earliest.

"Most likely Saturday. But it's all contingent upon how the ice affects the ship," said Anchorage Coast Guard spokesman David Mosley.

Colbath stressed the challenges the Russian tanker and US cutter have faced.

But she added: "It's an excellent learning opportunity for the Coast Guard, because we're really testing 'Healy''s capabilities, we're learning more about operating in this type of ice."

Having to work with different agencies -- and with Russians, via translators -- was also a new challenge, she said, while stressing that they "all have one goal, which is to get those critical fuel supplies to the residents of Nome."

Nome's winter woes are not the only ones making headlines in Alaska: in the town of Cordova, east of Anchorage, the National Guard has been called out after being buried under 15 feet (five meters) of snow, according to news reports.