The Pentagon acknowledged yesterday that it has held discussions with Saudi officials about an "integrated defense" for the Middle East that would include pre-positioning U.S. combat equipment there.

The Pentagon also conceded that there is an understanding that Saudi Arabia would let American forces use Saudi facilities to defend the Persian Gulf region.

But Defense Department spokesman Benjamin Welles repeatedly denied that there is any formal agreement covering these points and denounced a Washington Post story published Sunday as "foolish" because it implied that such an understanding had been slipped through without consultation with Congress. The Post article did not assert that there is any formal agreement covering these aspects of Saudi defense, but reported that the administration is pursuing a defense strategy for the Persian Gulf oil fields involving a regional air defense network and pre-positioned equipment for U.S. forces.

"The imputation that the United States government, the administration, has been seeking to slip by Congress, without fully apprising Congress of what we are trying to do as long-range strategy for the Middle East based upon the use of Saudi facilities, is in itself ludicrous," Welles said.

"Few transactions in modern U.S. history have been more visibly scrutinized by the Congress and the U.S. public than the AWACS sale," he said.

The Pentagon acknowledgements yesterday appeared to conflict with the statement issued Saturday on behalf of Defense Secretary Caspar W. Weinberger that he "flatly denies that the AWACS is the cornerstone of any larger program."

At yesterday's briefing in reaction to the Post story, Air Force Lt. Col. John Garrison read from a Pentagon "issue paper" which said that the sale of the airborne warning and control system planes "sets the stage for the development, with U.S backing, of a regional air defense system for the entire Gulf region. Saudi Arabia has taken the lead in the formation of the Gulf Cooperation Council," which includes five other moderate Gulf states. "The AWACS in its ground environment system affords the capability to link the air defense networks of these states into a unified system."

Garrison said that "the situation is one that we are convinced, and we are convinced that the Saudis are convinced, that given certain contingencies that may occur in the Southwest Asia-Persian Gulf region, specifically including the Soviet Union, that literally the only force that could meet the military requirements to deter and-or defend the region happens to be the forces of the United States.

"In that situation, we are convinced that the Saudis, for their own national security interests, will be anxious to have us assist them . . . . Clearly that is our understanding of the situation."

Welles said that "five or 10 years from now, we would hope to have an integrated air defense for the entire Middle East . . . to protect the Middle East from any possibility of aggression, by the Soviet Union or its surrogates" but denied there is any formal, written agreement and said it is "wrong to impute that we did have an agreement."

The Post article on Sunday said that the sale of AWACS planes to Saudi Arabia is one small piece of a grand defense strategy which is not incorporated in a formal agreement but was expressed in an explicit oral understanding reached last February in Saudi Arabia between military staff officers. While the strategy has not been approved by President Reagan, many of its parts are moving forward and their costs total between $35 billion and $60 billion.

Marine Col. Michael Sheridan, director of planning and requirements at the Pentagon, said he does not know of any agreements with the Saudis at present to allow the United States to pre-position combat equipment in their country. "What's been decided at the higher levels of government between the Saudi government and the U.S. government, I'm simply not privy to," he said.

Sheridan said the facilities that the United States is building elsewhere in the region for the Rapid Deployment Force are too far from the oil fields.

"So if we did have to go in there to defend Saudi Arabia, quite obviously we would like to use whatever facilities that they have," he said. "I think it's very prudent of the Saudi Arabian government to overbuild them. That's a damn good insurance policy."

Pentagon spokesmen denied that there was any formal agreement between the two countries regarding the sale of bomb racks or other advanced electrical equipment for the AWACS which Congress had been told would not be provided. "If at some point in time it were ever desired from this or future administrations' perspective to do something of that sort, it would have to go through the full process that the sale itself has gone through," Garrison said.

Garrison said that while Saudi Arabia is building facilities beyond its current military needs, it will need expanded capability in the future because it expects to have a much larger navy and as many as 160 fighter planes by the mid-1980s. Pentagon officials had previously told The Post that the new command, control and communications system for Saudi Arabia would be able to handle more than 360 fighter planes.