With one month remaining before U.S. base privileges in Turkey expire, U.S. and Turkish negotiators report considerable progress in talks about a new defense cooperation agreement.

Both sides, though, sound skeptical about the chances of achieving final settlement before Oct. 9 when the temporary status of the U.S. military presence in Turkey runs out.

While officials here and in Ankara expect that the bases will be permitted to continue their operations beyond the deadline -- Provided the talks do not break down -- pressures for an agreement are building on both governments.

The 26 U.S. military installations in Turkey -- reportedly responsible for collecting an estimated 30 percent of this country's intelligence about the Soviet Union -- have gained critical importance following the loss last winter of U.S. stations in Iran.

For TURKEY, the U.S. presence provides valuable leverage to win assistance for the improvement of its 500,000-man armed forces -- a key but at the moment weak link in NATO's southeastern flank.

But the current talks have been taking place in a political atmosphere in Ankara charged by the approach of national elections on Oct. 14. Not wanting to alienate leftist groups that have supported his left-of-center party, Turkish Prime Minister Bulent Ecevit has given no assurances about the future status of the U.S. bases.

Ecevit reactivated the bases temporarily last October after Congress lifted an arms embargo that had been imposed in 1974 when Turkey intervened in Cyprus.

"The Turks haven't threatened us," said a U.S. diplomat in Ankara yesterday. "But they haven't made any commitments either."

Negotiators reportedly are close to an accord on a "foundation agreement," the basic features of which reflect a compromise between the initial U.S. intention of signing no more than a simple agreement covering the operation of bases and Turkey's much broader desire to cement an economic and military relationship with the United States

Differences persist, however, on the precise wording of three supplemental agreements.

The most important of these involves the Turkish hope that the United States will pay a large part of the cost of modernizing Turkey's armed forces. The Turks have presented what on U.S. official described as a "hefty shopping list" for military hardware, worth between $2.5 billion and $3.6 billion over four years, depending on which government is counting.

In any case, U.S. negotiators say that Congress is not inclined to commit a definite amount for a specific time.

Another issue still being negotiated is a Turkish request for U.S. assistance in the development of an armament industry. A Pentagon team reportedly visited Turkey recently to scout possible businesses the United States might be able to assit in. The Turks also have asked the United States to pledge the purchase of a certain amount of Turkish-made armaments.

The precise rules for the operation of U.S. bases in Turkey also remain unresolved. The Turks would like all installations to be manned equally by Turkish and U.S. personnel, but U.S. negotiators note that Turkey does not have a pool of workers trained in modern electronics adequate to operate sophisticated U.S. equipment.

One further sticking point concerns the exact purpose to which the bases will be put. The Turks fear the United States might use the bases to move into the Middle East should events there require military intervention. They want the United States to stipulate that the bases will be committed only to NATO operations. U.S. negotiators are seeking vaguer wording, saying the bases "will be supporting the fulfillment of NATO commitments."

The head of the U.S. negotiating team has returned to Washington to review the U.S. position.

"In the last few weeks, we've made a lot of progress," said Alan Flanigan, in charge of Turkish affairs at the State Department. "But it is impossible to project at this time when there might be a complete agreement."