WASHINGTON (AP) - The Pentagon labeled its decision this week to hold off awarding a $35 billion Air Force refueling plane contract as a "cooling off" period in the bitter rivalry between defense contractors Northrop Grumman Corp. and Boeing Co. But with the lucrative deal still at stake, the dispute isn't likely to lose much heat.

Defense Secretary Robert Gates' plan to hand the politically fueled decision to the next administration means Boeing and Northrop will face each other again next year in a new competition for the right to build 179 planes and the possibility of many more.

Gates said he wanted to provide a new administration with "full flexibility," which analysts said will probably lead to a fresh start on the program that already has stretched seven years and featured several failed attempts to pick a winner. And it will almost certainly extend the battle the two major defense contractors have waged in Congress and through aggressive public relations campaigns.

"It will be very contentious," said Paul Nisbet, an aerospace analyst with JSA Research. "With a potential of $100 billion worth of business over the next 30 years, it won't be taken lightly."

The move by Gates erases the results of a tumultuous year in which Los Angeles-based Northrop won the contract, only to have bidding reopened after the Government Accountability Office upheld Boeing's complaints that it was unfairly awarded. Bidding was reopened, but Boeing threatened to back out last month and leave the Pentagon with just one bidder after seeing the new contract guidelines that appeared to favor Northrop's bigger plane.

How the two companies approach the upcoming round and what type of plane they propose depends on a range of factors, including who wins the presidency and whether the Defense Department changes its wish list for the aircraft's design and capabilities.

Boeing has to decide if it will offer a larger plane following indications that the Pentagon wants a plane that can carry more fuel. Gates' decision was seen as a reprieve for the Chicago-based company, giving it more time to revamp its proposal.

Analysts said Boeing could tender a bigger version of the jet based on the commercial 767 plane that it submitted originally. The company could also use variants of two of its other commercial jets - the larger long-range 777 plane and the mid-sized 787. Nisbet said that gives Boeing a wider range of options than Northrop when the Pentagon issues its new set of requirements for the contract.

Boeing spokesman Dan Beck said Thursday that the company will use the lull to do engineering and trade studies of different configurations of its planes. He would not give specifics on what was being considered.

"We think we will be in good shape in a timely manner to put together a proposal that will address the requirements," he said.

Northrop, which has partnered with Airbus parent European Aeronautic Defense and Space Co., must also determine whether to retool its proposal. The military version of the Airbus A330 that Northrop and EADS proposed was considered a favorite in part because it can carry 250,000 pounds of fuel, more than the 205,000 pounds hauled by Boeing's jet. Northrop spokesman Randy Belote said the company was waiting to see new program requirements before deciding how to proceed.

Defense analyst Loren Thompson of the Lexington Institute said Northrop will still hold an edge in the next round, especially if the Pentagon is looking for a larger plane. Boeing's big 777 could prove too lumbering to land at some military airfields and the 787 is still under development, he said.

Northrop's initial win earlier this year also is telling. "This is now Northrop's competition to lose," Thompson said.

The presidential election also could hurt Boeing's chances. Republican John McCain has been a sharp critic of Boeing's work on the tanker contract and has taken steps that helped Northrop in earlier rounds. Analysts said McCain could scale back the contract significantly, choosing to retrofit the existing fleet of planes.

Democrat Barack Obama has said he will seek a review of the tanker project, but it would probably be a lower priority for him, according to Richard Aboulafia, an aerospace analyst with the Teal Group.

Perhaps most unclear is when a new contract will be awarded. With changes in top officials at the Pentagon and White House, it could take until late next year for a winner to be picked. Some analysts said it could languish for several years.

What is clear is that the rancor between the two companies and their supporters will go on, Aboulafia said. Boeing and Northrop have run regular full-page newspaper ads touting their bids and rallied members of Congress on their behalf. Each has spent millions on Washington lobbying during the first half of the year.

The points of contention will still be present next year - fights over jobs, fear of EADS gaining a foothold in the U.S. defense market, political posturing in Congress and large sums of money at stake.

"Bitterness doesn't diminish, it usually accumulates," Aboulafia said.