The United States and Secretary of State Alexander M. Haig Jr. labeled a model for cooperation in the Middle East, yesterday signed a pact that allows the United States to help Egypt develop atomic energy for peaceful purposes.

The agreement includes the possible sale of nuclear reactors.

As explained by the State Department, the agreement basically culminates a process that began in 1974 when President Nixon offered to share peaceful atomic technology with Israel and Egypt.

In 1979, Israel decided not to accept because it would have to agree to inspection of its nuclear installations and various international agreements and safeguards meant to prevent peaceful techniques from being diverted to manufacture of atomic bombs.

Egypt now has agreed to ratify the nuclear nonproliferation treaty and has initialed a safeguards agreement with the International Atomic Energy Agency.

The new pact does not involve U.S. financial aid to Egypt, which has said it will put aside as much as $500 million a year from oil revenues to finance the start of its nuclear power program.

The agreement essentially sets up the conditions for cooperation, such as the possible sale by U.S. firms of nuclear reactors using "low-enriched uranium" fuel that could provide about 2,000 megawatts of electric power at the outset.

State Department officials point out that the agreement is similar in many respects to U.S. agreements with other countries and that the low-enriched fuel is not suitable for bomb production.

The Iraqi reactor bombed by Israeli planes June 7 was a research, as opposed to power, reactor that was supplied by France and used highly-enriched uranium fuel more susceptible to being diverted for weapons use.

Mather Abaza, Egypt's minister of electricity, described the new agreement as "another facet in Egyptian-American friendship . . . and in a just and lasting peace in the Middle East." Egypt has no intention of developing atomic weapons, Abaza said

In a related development, Charles N. Van Doren, former assistant director of the U.S. Arms Control and Disarmament Agency, reported yesterday that a study he made of the Iraqi nuclear program "uncovered no evidence of actual Iraqi efforts to develop or manufacture a nuclear explosive device."

Van Doren, a specialist in nuclear proliferation matters for 17 years, cautioned that he is not drawing conclusions about ultimate Iraqi intentions and that he separated his findings on Iraqi efforts from Iraqi "acquisition of materials and equipment that would in time have been capable of yielding enough special nuclear material to do so."

Van Doren told a news conference at the Arms Control Association yesterday that "certainly there is room for concern in the longer run." But, he said, the best Iraq could do, even theoretically, if it wanted to build a weapon in secret would be to accumulate enough nuclear material by various techniques to produce a bomb in one to three years.

Van Doren said it is "highly improbable" of uranium and changes in operation of the nuclear reactor required to produce a bomb could have escaped the notice of French technicians working at the Iraqi reactor site or IAEA inspectors.

The ACA also issued an unusally critical statement yesterday describing the Israeli air strike against the reactor as an action that "subverts" international efforts to bring nuclear developments under control and "invites retaliation."

Van Doren and ACA president Herbert Scoville Jr. aruged that nuclear research reactors, such as the Israeli facility at Dimona, which are not under international controls, are a greater problem than those in countries where external safeguards are permitted to function.

Scoville said ACA is not trying to defend what Iraq was doing but is trying to counter the charge that international groups such as IAEA are incompetent at spotting would-be abuses.

Van Doren's study, which he said was based on public information, not contacts with U.S. intelligence agencies, was the second major study of its king published here recently that cast doubt on Israeli President Menachem Begin's claims that Iraq was on the brink of secretly making nuclear weapons.

The other study, by the Congressional Research Service of the Library of Congress, is cited by senior State Department officials as closet to classified U.S. intelligence estimates of Iraq's ability to produce a bomb.

"On the whole," that study said, the Iraqi reactor "probably could not have been operated solely to produce plutonium [for bombs] without quick detection or withdrawal of the facility from the IAEA safeguard regime."

Even if it were withdrawn, production of as much as 20 kilograms of plutonium per year would have required "virtually perfect operation with no mistakes, breakdowns or unexpected technical problems," the study said.

So a lesser amount of plutonium would have been the more likely result and, the study said, after experimental needs and other factors, the amount remaining "probably would not soon have been enough . . . for a nuclear weapon."