Greece has agreed to accept an Airborne Warning and Control System aircraft from the North Atlantic Treaty Organization for surveillance of the alliance's southeastern flank by the end of next year, fulfilling a commitment made by the previous conservative government, according to well-informed Greek and NATO sources.

Greece agreed to participate in NATO's AWACS project before the 1981 election victory of Socialist Andreas Papandreou that ended conservative rule. The Socialists have chosen not to drop out of the project even though in the past three years they have questioned Greece's role in NATO's military wing and pursued an active policy of rapprochement toward the Soviet Union and its Warsaw Pact neighbors on the Balkan Peninsula, Bulgaria and Romania.

Political analysts here said one possible factor for this policy choice may be Turkey's participation in the AWACS project. Greece and Turkey are involved in a web of disputes in the Aegean Sea and over Cyprus, and both countries are lobbying for diplomatic support within NATO, and particularly in Washington, a supplier of arms and credits to both Athens and Ankara.

Just this Friday the Greek government reiterated its commitment to a project launched in early 1984 for the creation of a nuclear-free zone in the Balkans, with the participation of Bulgaria, Romania, Turkey and Yugoslavia. This would mean the removal of U.S. nuclear weapons from Greece.

One AWACS aircraft, a specially converted Boeing 707, will be rotated in and out of Preveza, the site of a Greek Air Force base, on Greece's western Ionian Sea coast, the sources said. Ground radar facilities there are being renovated to receive the aircraft.

The sources indicated that the AWACS will concentrate on Greece's northern border with Bulgaria. Greece also has a common northern border with Yugoslavia and Albania. The AWACS also will be deployed during NATO exercises in the region.

AWACS planes are particularly effective in detecting fighter aircraft flying at low altitude, below normal ground radar cover. The $2 billion NATO project that set up the AWACS force was launched in the 1970s and foresees the deployment of 18 AWACS by the end of 1985. A command headquarters for the AWACS force is located at Supreme Headquarters Allied Powers Europe in Belgium.

A main base at Geilenkirchen, West Germany, has been operating since 1982, with 12 AWACS already in place. Britain is deploying a separate force of 11 Nimrod surveillance aircraft at Waddington in eastern England. The Greek base will be one of three forward operating bases. The first, at Konya in southern Turkey, came into use in late 1983, while a second at Trapani, Italy, is scheduled to come into use by the end of 1985, along with Preveza.