Greek and U.S. commercial airline service between Athens and New York could be disrupted after next Feb. 6 unless there is a breakthrough in deadlocked negotiations to renew a 1946 civil aviation agreement that expires then, according to sources close to the talks.

Under the agreement's terms, the transatlantic Greek-U.S. market recently has been shared equally between Trans World Airlines and Olympic Airways. Last winter the Greek government gave the 12-month termination notice required by the agreement, denouncing it as "one-sided and colonial."

According to the sources, a first round of the negotiations collapsed in Washington in late September, after the United States rejected a Greek demand that only one U.S. airline be designated to serve Athens. No date has been set for a second round.

The American view is that multiple carrier designation -- which the present pact provides for -- is essential to ensure the maximum opportunity for U.S. airlines. According to the American side the only precedent for single-carrier designation is to be found in civil aviation agreements between the United States and some Communist countries.

The 1946 agreement allowed multiple unspecified carriers. But applications by Pan American, Transamerica and World Airways to serve Athens were turned down by Greece, according to U.S. sources.

"We support the U.S. government's negotiating position, but we hope the issue is kept realistic," a TWA spokesman in New York said today. "We are concerned that aviation issues should not be relegated behind other issues in the negotiations," he said, apparently referring to the cool relations between Washington and Greece's Socialist government, which some observers said may be hampering the progress of talks on a new pact.

Greek Foreign Ministry officials, however, said Athens is determined to protect the interests of Olympic Airways, the financially troubled national carrier that the government took over from the late Aristotle Onassis in the mid-1970s. The transatlantic route represented 20 percent of Olympic's international earnings in 1983.

"Greece is a very limited market, and we can't possibly compete with the American giants," one Olympic official said. "If it were opened to free competition, Olympic would disappear."