The Reagan administration yesterday responded to the Israeli bombing of an Iraqi nuclear reactor by suspending sale of four F16 fighter-bombers that had been scheduled for shipment to Israel this week.

But the administration, in a delicately worded letter by Secretary of State Alexander M. Haig Jr. to Senate Foreign Relations Committee Chairman Charles H. Percy (R-Ill.), stopped short of concluding that the Israelis had violated the 1952 Arms Export Control Act, which prohibits U.S. arms from being used for aggressive purposes.

Haig's letter said "that a substantial violation of the 1952 agreement may have occurred" and that the entire matter will be review by the U.S. government.

He said the review "will consider the contention of Israel that this action was necessary for its defense because the reactor was intended to produce atomic bombs and would become operational very soon. . . ."

The letter was the product of two days of intense discussion at the White House and State Department by top administration officials. It was drafted by Haig and, according to White House deputy press secretary Larry Speakes, "personally approved by the president."

Israel used F16s in its Sunday raid that destroyed the uranium-powered nuclear plant near Baghdad. Haig's letter took note of the Israeli claim that an attack would have been impossible once the reactor went into operation "because it could not be carried out without exposing the inhabitants of Baghdad to massive radioactive lethal fallout."

The administration action yesterday applied only to the four F16s that had been scheduled for shipment this week. At the White House, Speakes took pains to observe that the U.S. decision has no effect as of now on large military shipments to Israel he said would be in the pipeline by July.

There was a widespread impression at the White House and the State Department, where Haig's statement was simultaneously released, that yesterday's suspenson was likely to be both temporary and cosmetic. One well-placed source observed that Haig was departing on a two-week trip to the Far East and would be spared having to deal with the issue until after his return.

But the official Israeli response regarded the administration action as anything but cosmetic.

Israeli Ambassador Ephraim Evron expressed "deep regret and disappointment" at the administration's action, said Israel had acted in self-defense against a foe that has repeatedly vowed to destroy it and contended that it was "particularly regretful that the administration's punitive action was taken against an ally while Iraq. . . . has actively subverted and opposed American objectives in the Middle East."

Evron met with Haig shortly before the decision was announced.

State Department officials said that Faisal Alhegelan, the ambassador from Saudi Arabia, also made an unannounced all at the department yesterday, but the officials refused to say whether his visit was related to the U.S. effort to work out a solution that would be acceptable, if not embraced, by both the Arab and Israeli sides.

The Haig letter was described by one high-placed White House official as representing "a balanced judgment" that was sensitive to U.S. desires to stay on good terms with the contending forces in the Middle East.

Another White House official said the Reagan administration also was sensitive to the opinions of the American Jewish community, which was highly critical of the president's decision to sell sophisticated radar reconnaisance aircraft to the Saudis.

A Republican poll taken for the White House showed Reagan's popularity dropping among Jewish voters after the radar-plane decision.

In trying to negotiate its balancing act, the administration had to take into account the conflicting realities of the Middle East conflict. The United States is committed to Israel as an ally and has long been its principal arms supplier. But for the administration to ignore Israel's unprecedented action and Israeli Prime Minister Menachem Beginhs defiant vow to repeat such preemptive strikes against its enemies would seriously impair U.S. credibility and influence in the Arab world.

For this reason, sources said, the United States is likely to side with the Arabs if a resolution comes up in the United Nations Security Council that condemns the Israeli action without calling for reprisals. At the same, administration officials made it clear they would prefer that no resolution come up for a vote because it would put the United States in the position of making a judgment on an issue it says is under review.

"We haven't started seriously addressing the question of a U.N. meeting," a senior State Department official said last night. But, in reference to reports that the Arab bloc will seek a worldwide trade embargo against Israel, the official said, "We're against sanctions."

Among the officials who huddled yesterday with Reagan, Haig and the top team of White House advisers was U.N. Ambassador Jeane J. Kirkpatrick. Former secretary of state Henry A. Kissinger also met with the president, but his session came after the decision on the F16s was announced, and Speakes said, without elaboration, that the purpose was another subject.

Under the law the president or Congress, by joint resolution of both houses, theoretically could suspend or otherwise limit military aid to Israel if it is determined that the Israelis violated their agreement to use U.S. arms only in self-defense. However, a senior State Department official made clear that no action is required.

That was what the Carter administration did two years ago when, responding to a congressional complaint, it found that Israel might have violated the terms of the agreement in its military activities in Lebanon.

Percy said the Foreign Relations Committee probably will hold hearings next Wednesday or Thursday on the administration decision. He told reporters he supports the decision but warned that "this is a grave matter and has, obviously, deep impact on the United States and the role it is playing in the Middle East."

Generally, the first congressional response to suspension of the sale was positive. Rep. Clement J. Zablocki (D-Wis.), chairman of the House Foreign Affairs Committee, called the decision "a measured and prudent one; it is also necessary."

"Mr. Reagan . . . has said what we as Americans have always believed -- laws must be obeyed, agreements must be observed."