President Reagan must decide by Friday whether to go ahead with the scheduled delivery of four more F16 fighter-bombers to Israel, the Pentagon said yesterday, even as Israel's weekend air raid on Iraq's nuclear power plant threatened to build into one of the biggest crises of his young administration.

Asked if Reagan would hold up delivery of the additional F16s as part of the U.S. protest of Sunday's surprise strike, Pentagon spokesman Henry E. Catto Jr. said: "It's too early to tell. I can't rule it in; I can't rule it out."

The president and his principal national security advisers met for 1 1/2 hours late yesterday to discuss the situation. No announcements were made about the discussions, but Secretary of State Alexander M. Haig Jr. said afterward that "no decisions of any kind" were made about the F16s awaiting shipment to Israel.

Haig said that a report by the administration on whether Israel violated U.S. laws in using American-supplied aircraft to attack the Iraqi installation should be ready in 24 to 48 hours.

Eight F16 fighter-bombers, accompanied by six F15 escorts, dropped 2,000-pound bombs Sunday on the Iraqi nuclear research facility at Tuwaitha, about 12 miles southeast of Baghdad, destroying a French-built nuclear reactor.

Reagan's decision on delivery of the additional F16s may become a rallying point in the debate over whether the Israeli raid was legitimate self-defense against a grave nuclear threat or an outlaw act in violation of agreements on the use of American-supplied weapons.

Condemnation of the raid came from several members of Congress, although others defended it.

"One of the most provocative, ill-timed and internationally illegal actions taken in that nation's history," said Chairman Mark O. Hatfield (R-Ore.) of the Senate Appropriations Committee, which has considerable leverage over how much military aid goes to Israel.

"Israel's sneak attack . . . was an act of inexcusable and short-sighted aggression," The New York Times said in its lead editorial. "Israel's ever-widening definition of self-defense is illusory. Israel risks becoming its own worst enemy."

But Senate Minority Whip Alan Cranston (D-Calif.), in defending the action, said Israel looked upon "the pre-emptive first strike as essential to her security. . . . I've been warning about the existence and development of a nuclear reactor in Iraq, and since the United States government was unable or unwilling to persuade France and Italy to halt their transfer of highly sensitive nuclear technology to Iraq, I think it was inevitable that this sort of an action would occur."

Israeli Prime Minister Menachem Begin wrote Reagan about the raid, White House officials said, but the contents of the private letter were not divulged. Reagan was informed of the attack by national security adviser Richard V. Allen on Sunday afternoon, a full day before the administration condemned it. A White House spokesman, when asked, said yesterday he did not know why the administration's reaction was delayed 24 hours.

Catto, in giving the first official details of the military nature of the bombing, said "the Israelis tell us that there were F15s -- six of them -- and F16s -- eight of them -- involved. The F16s did the bombing. The F15s were used as protective cover."

The two-seat F15 and the single-seat F16 are among the most sophisticated warplanes in the sky. With its powerful radar, the F15 can see farther than its adversaries can, a key advantage in aerial combat, and it is armed with the latest missiles for dog-fighting. The F16 has sophisticated electronic equipment for pinpoint accuracy in dropping blockbusters such as the 2,000-pound bombs that fell on the Iraqi plant.

Before Catto's briefing, there had been reports that Israel had employed its older F4 fighter-bombers. Catto also spiked reports that Israel had used so-called "smart" weapons against the nuclear plant. "They apparently were 2,000-pound bombs used, so-called dumb bombs; iron bombs," he said.

The key question confronting Reagan, Catto indicated, is not whether Israel violated arms-sales agreements, but by how much. Those agreements restrict Israel's use of American-supplied weapons to national and regional defense.

Said Catto:

"If the violation is found to be substantial," Israel "will be ineligible for future deliveries" of arms. "The law doesn't spell out substantial. That becomes a matter of art, not science, so that's a subjective judgment that has to be made."

Catto also spotlighted another loophole available to Reagan, saying: "The president can find that U.S. security would be adversely affected by such a cutoff, in which case he can continue to make deliveries."

Batting the ball into Congress' court, he added: "If a joint resolution is passed by Congress determining that there is substantial violation, deliveries can be finally and permanently cut off."

Senate Minority Leader Robert C. Bryd (D-W.Va.) said yesterday that he was "a little amazed" that U.S. intelligence did not detect the raid, noting that four AWACS (airborne warning and control system) sentry planes are on duty in Saudi Arabia.

"It seems to me we should have been able to get something on this," he said.

At the Pentagon, Catto rejected the idea that the United States had suffered an intelligence gap. "There is no concern that U.S. intelligence has in any way, shape or form failed," he said.

"There was no way in the world for the AWACS to have picked this up. It was simply too far away. The AWACS mission is aimed strictly at the Arabian Gulf, not toward the north. It was carrying out its mission. There was not a single solitary blip.

"The raid apparently took place Sunday morning about 11:30. We found out about it at 1540 [3:40 p.m.] that Sunday afternoon when the American Embassy in Tel Aviv was informed."

Defense Secretary Caspar W. Weinberger "had absolutely no foreknowledge" of the raid and believes it will make peace efforts in the Middle East "measurably more difficult," Catto said.

Weinberger has directed Pentagon lawyers to determine whether Israel violated the Foreign Military Sales Act, but their findings may not be in hand by Friday, when the four new F16s are to be delivered.

To date, Israel has ordered 75 F16s, 53 have been delivered. Israel also has ordered 40 F15s, of which 25 have been delivered.