The United States will lose a key electronic surveillance station on the island of Crete if Greece, under its new socialist prime minister, forces US bases off its territory, sources say here.
Andreas Papandreou and the Panhellenic Socialist Movement (Pasok) swept to power Oct. 18 in a campaign that called for the ouster of US bases from Greek soil and for Greece's withdrawal from the NATO alliance. ''Foreign bases have no place in our country,'' declared the Pasok platform.
If Mr. Papandreou hews to Pasok's position on foreign bases - which is by no means a foregone conclusion, according to sources here - a total of four US installations would have to be dismantled. They are:
* The Heraklion air station on Crete.
* The fleet support and naval air facility at Suda Bay, also on Crete.
* The US Navy communications station at Nea Makri near Athens.
* Hellenikon Air Base outside the Greek capital.
According to defense experts here, the Heraklion base, manned by the US Air Force, monitors the communications of ships and aircraft in the Eastern Mediterranean for the supersecret National Security Agency (NSA) which specializes in communications intelligence and the making and breaking of codes.
Essentially, says a diplomatic source, the Heraklion air station, sometimes referred to as an Air Force communications center, ''keeps tabs'' on ships and aircraft.
The loss of all four US bases in Greece would pose Pentagon planners with a ''substantial short-run problem,'' according to a source who asked not to be identified. ''But it wouldn't be devastating,'' he adds.
The US, in the opinion of some analysts, would be compelled to seek alternative sites for its Greek bases should they be closed down. ''It takes time to make substitutions, to make arrangements with host governments,'' declares the source. ''We'd be winging it until that is achieved.''
He suggests that Washington should explore whether the new Greek premier (a former economics professor at the University of California, Berkeley) can ''be eased off his more bellicose campaign pronouncements,'' while at the same time examine alternative sites for the bases currently in Greece. These might be relocated in Turkey, Egypt, or even Israel, in the view of some analysts.
If Andreas Papandreou does take Greece out of NATO (the Pasok platform aims at the ''dissolution'' of both the Atlantic Alliance and the Warsaw Pact) the effect would probably not be catastrophic from a military point of view, say analysts. NATO forces would presumably be denied facilities at Suda Bay along with access to a missile-firing range on the northwestern coast of Crete they have used for some years. In addition, the five so-called NADGE (For NATO Air Defense Ground Environment) aircraft early-warning radar sites on Greek territory would face an uncertain future. Even if they continue to function under Greek control, some analysts worry that the radar data from them may not be passed on to NATO.
Even so, the possible loss of them should not prove crucial, according to some analysts. For example, John M. Collins, the senior specialist in national defense at the Library of Congress, says the role of Greek (and, for that matter , Turkish) forces in NATO's plans is simply to reduce freedom of action for Soviet reserves in the southern USSR. ''Airfields, NADGE installations, and most communications sites are only significant locally,'' he declares, adding that ''Aegean ports improve the Sixth Fleet's posture in the eastern Mediterranean, but are not crucial beyond that basin.''
Because, in the opinion of experts, Greece's chief value to NATO lies in its provision of bases for US forces - rather than in any military might of its own - its absence from the alliance could be counterbalanced by the relocation of Greek-based US forces into neighboring, allied countries.
But although Papandreou has campaigned on a platform that seeks the ejection of US forces from Greece, he has yet to implement his electoral pledge. ''There is a difference in tone between pre-election and post-election,'' declares an observer of the Greek political scene.