Islamabad, Pakistan — The F-16 supersonic fighter planes the United States proposes to sell Pakistan now seem as important a symbol in the trouble Indian subcontinent as earlier AWACS aircraft sales did in the Gulf and Middle East.
''In this region the F-16s have become as much a symbol as the AWACS were in the Middle East,'' says a knowledgeable Western diplomat. Like many Pakistani and diplomatic officials here, he expects President Ronald Reagan and Secretary of State Alexander M. Haig Jr. to go down the line for the Pakistan plane sales should Congress act to block them in the two weeks it has left to do so.
Should the F-16 sales fall through, many analysts here fear, the growing US-Pakistan relationship would quickly crumble. Pakistan could well succumb to Soviet military pressures to settle down to accommodation with the Russian-backed Babrak Karmal regime next door in Afghanistan, they believe.
As with most symbols, the F-16s have multiple meanings that vary with the eyes of the beholders.
Politically, as both Pakistani and American officials see it, the F-16s are a key test of America's commitment to shore up Pakistan as an anticommunist bulwark and front-line state in the wake of the December 1979 Soviet invasion of Afghanistan.
Implied is American support for the martial law regime of President Zia ul-Haq, who came to power in a 1977 coup, hanged his predecessor Zulfikar Ali Bhutto, and canceled out on promised elections. His rule has achieved at best a middling acceptance, neither popular nor unpopular.
Regionally, the F-16s have come to symbolize the US willingness to cast its lot with Pakistan over the strong objections of India - which fears the planes will ultimately be aimed eastward against it.
Both Pakistani and American officials have professed themselves mystified by India's sense of vulnerability, given its victories in past Indo-Pakistani wars. These officials say the F-16s will not affect the regional military balance heavily weighted in India's favor.
Militarily, says a high Pakistani official who declined to be identified, ''the F-16s will give (Pakistan) a lot of deterrence.'' He referred to the frequent air incursions from across the Afghanistan border, which Pakistan says total up to 379 over the last two and a half years.
''The F-16s will slow down the air violations,'' predicts Noor Ahmad Husain, director general of the Institute of Strategic Studies in Islamabad. ''They will strike the fear of God ( in our neighbors). We can react with our present aircraft but it isn't the same thing.
''What's more,'' he adds, ''it's going to be good for the morale of the Air Force and the country. As a front-line state we certainly don't want to use these things for aggression but we certainly can't abjure the right of self-defense. The Russians respect people who can hit back - basically they're bullies. Once they know they can get hurt, they are twice as careful.''
Much the same theme has been sounded by James L. Buckley, US undersecretary of state for security assistance, in congressional testimony earlier this fall. The F-16s will both give Pakistan the ability to deal with cross-border threats and ''keep the Soviets from thinking that they can coerce, subvert, or intimidate Pakistan with impunity,'' according to Mr. Buckley.
Such deterrence, though, would be mainly psychological - only six of the 40 F-16s the US proposes to sell Pakistan over several years will be available within the next 12 months. The planes will also spend most of their time parked on the ground, since US officials have said they can log only six to eight air hours a month until local pilots are trained and ground support systems and equipment set up.
Nevertheless, the F-16s are a crucial first test of the American commitment to Pakistan - which includes a $3.2 billion aid package, about evenly divided between military credits and economic aid, over five years.
The aid package starts out modestly with only $100 million proposed for this fiscal year in economic assistance, and increments will require annual congressional budgetary action. But the F-16 deal, intended as a cash sale, is different - both houses of Congress would have to specifically disapprove it within a 30-day period now halfway up. Neither has acted yet.
The cash sale terms pose another test - of financially strapped Pakistan's ability to round up the funds to pay its airplane bills from friendly Islamic nations. Senior Pakistani officials have publicly anticipated financial help from what they call ''our Islamic friends'' - mainly Saudi Arabia - to foot the bill, estimated at $1 to $1.2 billion for the full 40-plane package.
To date, diplomatic observers in the Pakistan capital see no evidence that any money has come in for the first installment of six F-16s. However, one notes , ''the Pakistanis are working on it very hard.''
A current common expectation is that Saudi Arabia will make a half-billion-dollar kitty available to Pakistan for the F-16s. But that means, analysts point out, that Pakistan may have to dip heavily into its anticipated US military credits to round out the full complement of 40 planes - leaving not much to modernize its obsolete ground equipment.
''More than half the money (in US military credits) is going to be spent on 40 F-16s, which is crazy,'' comments a seasoned Western diplomat. ''They could get so much of the other things they need if it weren't for the F-16s. I don't think it makes much military sense.''