WASHINGTON — Washington state lawmakers are backing a bid by Boeing Co. for more time to bid on a $35 billion contract to build aerial refueling tankers for the Air Force.

Boeing said Friday it is considering bailing out of the politically charged competition if it does not receive an additional four months from the Pentagon to assemble its offer.

“More time should be given to guarantee that all the bidders can provide the Air Force with the best options possible,” said Sen. Maria Cantwell, D-Wash.

The tanker contract is one of the largest in the history of the Pentagon, and requiring bids by October “is just inadequate,” Cantwell said.

Rep. Norm Dicks, D-Wash., said it would be unfair for the Pentagon to hold a competition for a larger tanker than it initially sought without allowing adequate time for Boeing to revise its proposal.

“Given the delays already caused by the Air Force’s own flawed selection process, the request for additional time to prepare a proposal based on a different aircraft is entirely reasonable, and it should be granted,” Dicks said.

“These planes will be in the fleet for 40 to 60 years, and it’s more important to make the right decision” than to make a choice by the end of the year, Dicks said.

Boeing lost the initial round in February to Northrop Grumman Corp. and its partner, Airbus parent European Aeronautic Defence and Space Co. The competition was reopened last month after government auditors found “significant errors” in the Air Force’s decision.

The revamped competition is focused on eight areas where the Government Accountability Office found problems with the initial process.

Northrop Grumman Chief Operating Officer and President Wes Bush criticized Boeing’s request for additional time, saying it will only cause more delays and higher costs for the taxpayer.

Sen. Patty Murray, D-Wash., said that because of major changes made by the Pentagon to its draft bid request, both companies deserve more time to respond.

“This is a $40 billion contract to design and build the backbone of our nation’s military might, and the requirements have changed overnight,” Murray said in a statement. “The draft RFP clearly favors a larger plane.

“Providing only 60 days for a major design overhaul not only skews the competition toward Airbus but also breaks the promise of a fair competition for our military and taxpayers.”

Murray and other Washington lawmakers say the Pentagon appears biased against Boeing as it seeks bids to build 179 aerial refueling tankers to replace the Air Force’s aging fleet.

Kansas Republican Sens. Pat Roberts and Sam Brownback agreed, saying they also support Boeing’s request because the specifications appear to support Northrop Grumman.

A revised proposal announced earlier this month — the latest in a six-year effort to secure new tankers — seems to favor the design offered by Northrop Grumman, they say. The lawmakers have threatened congressional action if they are not satisfied that the revised competition is fair and transparent.

Chicago-based Boeing has supplied refueling tankers to the Air Force for decades. It proposed building new tankers based on the 767 commercial jetliner in Everett and modifying the planes for military use in Wichita, Kan.

The Northrop plane, based on the Airbus 330, would be assembled in Alabama.