The country's only two heavy-duty icebreaker ships are old and broken, and Congress and the White House are at odds over how to respond as the melting of polar ice increases the economic and security stakes in the Arctic region.

The House on Friday was working on a Coast Guard spending bill that would decommission the Polar Star, slated to be the last somewhat seaworthy icebreaker after its sister ship, the Polar Sea, goes out of service in the near future.

The White House, in a statement issued Thursday, said it "strongly opposes" the legislation because decommissioning the Polar Star would "create a significant gap in the nation's icebreaking capacity."

In the Senate, Sen. Maria Cantwell, D-Wash., is trying to block the decommissioning of either ship with a provision she added to a Coast Guard bill. The ships are based in the Seattle area and support hundreds of jobs there.

"Our nation needs icebreakers," she said at the committee meeting. "With Russia moving many troops to the Arctic, and Chinese investors buying parts of Greenland, this is also a national security issue."

There's little disagreement on the need for a U.S. presence in the Arctic. The Congressional Research Service, in a report last year, said the shrinking of the icecap will result in increased commercial and military ship activity and greater exploration for oil and other resources.

That calls into demand the functions of icebreakers: defending U.S. sovereignty and economic interests, monitoring sea traffic, law enforcement, conducting search and rescue operations and scientific research.

"We desperately need the Coast Guard and the administration to do what we have asked them to do really now for more than 10 years _ define what our mission is in the Arctic," said Rep. Frank LoBiondo, R-N.J., chairman of the House Transportation and Infrastructure Committee's Coast Guard subcommittee.

He said it costs tens of millions of dollars a year to keep the two vessels tied up at the dock, and he hopes the House move to take them out of service will push the administration into deciding how large a fleet is needed in the future.

The lone Alaska congressmen, Republican Don Young, opposes decommissioning icebreakers and wants to increase the number of vessels in any way possible, spokesman Luke Miller said. Young has introduced a bill that would authorize the Coast Guard to enter into long-term lease agreements for two new icebreakers.

The icebreakers are supposed to have a 30-year service life. The Polar Star, commissioned in 1976, is docked in Seattle, in caretaker status since 2006. The Polar Sea, commissioned in 1978, suffered an engine breakdown last year and has been out of service. The Coast Guard also has a third, medium-duty icebreaker, the Healy, that is used mainly for scientific research.

The White House said Congress has previously approved funds to reactivate the Polar Star by the end of next year, extending the life of the ship for seven to 10 years. That, it said, "will stabilize the United States' existing polar fleet until long-term icebreaking capability requirements are finalized."

Cantwell cited estimates that the Coast Guard needs a minimum of six heavy-duty icebreakers and four medium-duty icebreakers to meet Coast Guard and Navy mission requirements.

That still wouldn't match Russia. The Congressional Research Service said last year that one estimate put the Russian fleet at 25, including six active heavy icebreakers. Finland and Sweden each had seven icebreakers, and Canada six, it said.

The CRS also put the cost of extending the service life of the existing ships for 25 years at about $400 million a ship, in 2008 dollars. It said that replacement ships might cost $800 million to $925 million.

Cantwell said refurbishing a vessel would take five years and employ more than 300 workers, while rebuilding it could take eight years and employ more than 1,000 workers.