The devastating Gulf of Mexico oil spill has heightened fears of a similar disaster occurring off the Arctic coast when long-planned exploratory drilling is due to get under way later this year.

Environmental activists are calling on US Interior Secretary Ken Salazar to halt Shell Oil's plans to begin exploratory drilling in the Chukchi and Beaufort Seas off the coast of Alaska in July.

Salazar is expected to make a final decision sometime after May 28 following completion of a safety review ordered by President Barack Obama.

Shell received a boost last week when an appeals court rejected claims by environmentalists that the federal Minerals Management Service (MMS) had erred when it gave preliminary approval to the oil giant's plans.

"Shell is committed to undertaking a safe and environmentally responsible exploration program in the Chukchi Sea and Beaufort Sea in 2010," Shell President Marvin Odum said in a letter to the MMS released Monday.

"I am confident that we are ready to conduct the program safely, and, I want to be clear, the accountability for this program rests with Shell."

Activists have said the remote nature of the proposed exploratory drilling site, sub-zero temperatures and gale-force winds would make be formidable obstacles to any potential clean-up operation.

The Alaska Wilderness League's executive director Cindy Shogan said in a statement that it would be almost impossible to mount the kind of clean-up witnessed in the Gulf of Mexico, describing the Arctic as one of the "most remote and extreme environments on Earth."

Shogan said 32 vessels were able to respond to the Gulf leak within 24 hours. "In the Arctic, that number is 13," she said.

"Likewise the skimming capacity in the Gulf was 171,000 barrels a day; in the Arctic it would be 24,000 barrels a day.

"And while it's 47 miles from the Louisiana coast to the site of the Gulf spill, in the Chukchi Sea the nearest dock is 250 miles from the proposed well sites, with clean-up equipment stationed even farther away."

In its letter outlining plans to deal with any possible spill, Shell said it would have a giant "coffer dam" ready to be deployed within an hour of a possible blow-out, while dispersant would be applied immediately to staunch the flow of oil. Teams of divers and a remote submersible would also be on hand.

However Rebecca Noblin, Alaska Director for the Center for Biological Diversity, said Shell's proposed contingency plans showed "a basic lack of respect for how dangerous the Arctic environment actually is."

"They've put forth this idea that it would be easier to clean an oil spill in icy waters and that is completely untenable," Noblin told AFP.

"If there were to be an oil spill in the Arctic it would be extremely hard to mobilize the people and the boats and the helicopters and everything you need to respond.

"In the Gulf they've had more than 10,000 people, hundreds of boats. In the Arctic it would be dozens of boats and a few hundred people. They'd have to fly people in. And even then there might not be enough places to house them."

Activists say a spill in the Arctic similar to the Deepwater Horizon disaster could also wreak havoc with the region's Alaskan Native communities and unique wildlife.

"Polar bears are already in trouble and an oil spill could be the difference between survival and extinction," Noblin said.

Martha I Falk, a representative of the Inupiat tribe from the 4,500-strong coastal town of Barrow, told a briefing in Washington on Thursday that the community would not be able to cope with a major oil spill.

Falk had just returned from a visit to witness the clean-up operation in Alabama. "If an oil spill were to occur in Arctic waters there is no proven technology to respond or recover," Falk said. "This would impact our whales, bearded seals, polar bears and ecosystems."