East Meets West at NATO Headquarters : Military: Former Warsaw Pact enemies are daily visitors to the defense alliance’s offices. The thaw began last year.

Not long ago, Hungarian diplomat Tibor Kiss regarded the fenced-in, low-slung headquarters of the North Atlantic Treaty Organization here as a forbidding fortress--definitely off limits to East European officials.

But times have changed, and today Kiss, the embassy’s No. 2 man, finds himself invited often to NATO to talk to officials there on a wide range of political and security matters.

A genial diplomat who favors blue blazers and speaks English, French and Flemish, Kiss sipped coffee in his high-ceilinged, spacious old office here and observed: “The extent of our contact is quite amazing. I’m in constant touch with NATO officials. . . .”

And if the East European diplomats such as Kiss don’t exactly have the run of the place, they do, in the words of an American official, “get into high-security areas where they would have been totally barred.” And a senior NATO officer added: “I’d say there’s some kind of meeting here with Eastern Europeans almost every day--and that’s not including telephone calls.”

The new liaison between the 16-member NATO and its onetime adversaries in the now-disbanded Warsaw Pact began after the London summit of 1990, when NATO decided that it was time to make contact with the Soviet Union, Poland, Czechoslovakia, Hungary, Bulgaria and Romania.

The contact has now been widened to include the three newly independent Baltic states of Lithuania, Latvia and Estonia. NATO’s Rome summit in November created the North Atlantic Cooperation Council, which provides for regular meetings of 25 foreign ministers. The first is scheduled for Friday.

Most East European embassies have designated their ambassadors to Belgium, based in Brussels, as their official liaison with NATO and have appointed an official such as Hungary’s Kiss to oversee day-to-day relations.

“Our problem after the collapse of communism and breakup of the Warsaw Pact was to search for security,” explained Kiss. “So we are exploring all sorts of ideas with NATO. We would like security guarantees and to become NATO members--but we realize that won’t happen right away.”

The East-West contacts cover a wide range of security matters, ranging from the broadly political to the highly technical, such as defense subjects. After every major NATO meeting, the East Europeans are called in to be briefed on the salient points. When U.S. officials visit NATO headquarters, the Americans hold special background briefings for East Europeans.

Finally, the Easterners can discuss specific topics that concern them by merely phoning NATO for an appointment. During the abortive coup against Soviet President Mikhail S. Gorbachev last August, for instance, Soviet diplomat Mikhail Timochkin left the Soviet compound on Brussels’ southern outskirts to visit NATO--to learn that the alliance did not approve of a Gorbachev overthrow.

And during the Baltic crisis last January, NATO’s Secretary General Manfred Woerner made it plain to the Soviet ambassador that the alliance would be very unhappy, if Soviet troops were used to quell peaceful demonstrations.

“We told them we expected them to comply with the terms of the Conference on Security and Cooperation in Europe,” said a NATO diplomat, “and we think we may have had some influence then.”

Another senior NATO official observed: “The Russians have been very keen to establish strong relations with NATO. We are, too, not the least to show them we are not favoring their former Warsaw Pact allies over themselves. The Soviets are coming to realize that NATO is good for the stability of all of Europe, and they, too, are beneficiaries of this fact. And they are interested in our reaction to the formation of the new Slavic commonwealth.”

Besides specific meetings between East European and NATO diplomats, there is a range of other contacts, including NATO briefings for visiting Eastern delegations plus workshops and seminars on security matters. NATO now briefs delegations from such organizations as the Hungarian Youth Organization, the Soviet Assn. of Political and Military Studies and the Romanian Parliamentarians and Academics.

“We have even briefed Soviet economists here,” observed a NATO official. “We know a lot more about the Soviet economy than they do.”

Most East European diplomats here believe that the Rome NATO summit declaration establishing the North Atlantic Cooperation Council will further cement relations between East and West.