Coast Guard Commandant Admiral Robert Papp made the decision Thursday after meeting with Sens. Maria Cantwell of Washington and Mark Begich and Lisa Murkowski of Alaska, the senators said Friday.
"The Polar Sea's hull is still in sound condition," Cantwell said. "Postponing its scrapping allows the administration and Congress more time to consider all options for fulfilling the nation's critical icebreaking missions."
The United States needs more icebreakers in the Arctic, the Alaska senators said.
"While this may only be a six-month respite for the Polar Sea, I will use this period to work through my role on the Appropriations Committee to make America's icebreaking capacity a top priority," Murkowski said.
The 399-foot Polar Sea is 35 years old and has been out of service since an engine failure in 2010. It had been scheduled to be dry-docked Monday for the first steps in demolition.
Its 36-year-old sister ship, the Polar Star, has been on caretaker status since 2006 and undergoing a $57 million upgrade. The rehabbed Polar Star is expected to return to service next year.
The United States currently has only one working icebreaker, the Healy. It was used last winter to escort a Russian tanker to Nome to make an emergency delivery after a fuel barge failed to arrive before the Bering Sea froze.
The Healy is a medium-duty icebreaker designed to crush ice about 5 feet thick. The Polar Sea is designed to break through ice up to 21 feet thick.
One Coast Guard study said the agency and the Navy need six heavy duty icebreakers and four medium icebreakers, the senators said. The reduction in Arctic ice has created more opportunities for Northwest Passage trade, fishing and oil exploration, as well as more environmental and security concerns. The icebreakers also travel to Antarctica to resupply McMurdo Station.
The hull is the costliest part of an icebreaker to build, said Brian Baird, a former Washington congressman who is now vice president of Vigor Industrial, formerly Todd Shipyards, which repairs the icebreakers. Building a new icebreaker could take 10 years and cost more than $800 million, Baird told The Seattle Times.