KOTZEBUE, United States (AFP) - President Barack Obama blazed a new trail as US leader on Wednesday, becoming the first to head above the Arctic circle to urge Americans to take swift action against climate change.

"There is one thing no American president had done before and this is travel above the Arctic circle," Obama said at the school gym in Kotzebue, a small Alaskan town of 3,000. "I could not be prouder to be the first," he added with a smile.

Touching on his call for urgent efforts to curb global warming, his main focus since his Alaska visit began on Monday, Obama said Alaskans were already living with evidence of the changes.

"In the past few years I have been trying to make the rest of the country more aware of climate change. But you are already living it," the president said.

"What's happening here is America's wake up call, it should be the world's wake up call," Obama said. "We are not moving fast enough. The effects can be irreversible if we do not act."

Obama is in Alaska to build support for domestic carbon reduction rules and an international pact to cap global temperature increases.

In December, representatives from around the world will gather in Paris to try to thrash out a deal to limit rises to two deg C over pre-industrial levels.

The United States is the world's second biggest emitter of gases that play a lead role in global warming, after China.