NEW YORK (AP) _ Trans World Airlines Inc.'s offer to merge with Pan Am Corp. raises new questions about troubled Pan Am's immediate future, but analysts said Monday they doubted the deal would fly.

''As far as I can see, it's sort of hazy at the moment,'' said Thomas Canning, at Standard & Poor's. ''We've got to wait for the reaction from Pan Am. For their fiduciary duties, they have to consider it.''

Analysts said Pan Am will probably proceed with plans to sell prized London routes to UAL Corp. in a $400 million deal that also includes a cooperative marketing agreement. The airlines would coordinate flights and feed passengers to each other.

Pan Am said that the UAL deal, which is supposed to be completed by Wednesday, was its current ''focus.'' But Pan Am refused to comment on the merits or status of TWA's offer, made Friday in a letter from TWA Chairman Carl C. Icahn to Pan Am Chairman Thomas G. Plaskett.

''We are not going to comment on whether or not we have had any communications with Mr. Icahn since we have received his letter,'' Pan Am spokeswoman Pamela Hanlon said.

She said, however, that Pan Am understood Icahn's offer would only come into play if the agreement with UAL is not completed Wednesday.

''It is a binding agreement and (the TWA offer) certainly does not change that agreement,'' Hanlon said. But the UAL deal does not prevent Pan Am from discussing a merger, she said.

UAL refused to say whether it believes the TWA offer jeopardizes its pact with Pan Am. ''Talk to Pan Am,'' spokesman Joe Hopkins said.

Icahn proposed offering about $150 million in cash and securities with a face value of $300 million for Pan Am. Since the cash value of the securities would vary, analysts were uncertain whether Pan Am stockholders would gain money or lose money through the transaction.

Pan Am stock rose 1/4 to 1 7/8 in active trading Monday.

Pan Am and TWA are the only U.S. carriers to fly into London's Heathrow Airport, the most desirable destination in the city that is considered the gateway to Europe. Analysts predicted a TWA-Pan AM merger would face regulatory troubles because the government would not want to see all of those routes fall into the same corporate hands.

AMR Corp., the parent of American Airlines, has said it would pay in excess of $500 million for the London routes, but Pan Am said it was not interested in merely selling the routes. Pan Am said its marketing arrangement with UAL would help build up its Latin American service with flights connecting through Miami.

Analysts said a TWA-Pan Am merger would likely benefit both carriers, considered among the weakest in an industry that has been hit hard by rising fuel costs and sluggish demand for travel.

''It would make for a stronger carrier. They would have the strength of the Atlantic, with the Pan Am Latin American routes,'' Canning said.

Even if no serious merger talks are held, the publicity surrounding Icahn's offer has probably helped both both airlines, according to an analyst with said Icahn might have other motives.

''What you see isn't what you get with this guy,'' said Kevin Murphy, of Morgan Stanley.

''If he can prevent United Airlines from going into London, that would prevent a more formidable carrier from going into Heathrow,'' Murphy said. ''By creating more market forces for international assets and routes, that can only come back and help him, should he also decide to sell assets.''

Without a merger with Pan Am, TWA will be left in a position where it either needs to buy assets, such as the Atlanta hub and Miami overhaul base of Eastern Airlines that it has expressed an interest in, or sell its own assets, analysts said.

The head of the TWA branch of the Air Line Pilots Association, Kent Scott, agreed.

''I think this is Icahn's way of stirring up interest in TWA and saying 'Hey, I want to do a deal, whether it's buy, sell or whatever,''' Scott said.

Analysts say it was too soon to say whether the TWA offer could spark any reshuffling that would involve more than two airlines. They doubted the deal could enable Pan Am to seek better terms from UAL, because the important aspects of that deal had already been settled.