President Reagan said Tuesday "it seems to be quieting down" in the Persian Gulf after a round of sea and air battles Monday in which the United States dealt a heavy blow to Iranian forces.

"We hope it continues that way," Reagan told reporters during a photo-taking session at the start of a meeting with Republican members of Congress.Iran took a licking when it tried to strike back after the United States destroyed two Iranian oil platforms. In the most intense exchanges since Reagan beefed up U.S. firepower in the gulf last summer, American forces sank or damaged four Iranian attack boats and disabled two frigates that fired missiles at U.S. planes.

Asked if the United States had underestimated what the Iranian response would be, Reagan replied: "No."

"It seems to be quieting down. We hope it continues that way," Reagan said.

Reagan said nine ships were involved in a search-and-rescue mission for a U.S. Marine helicopter missing with two crewmen from Monday's operation. The attack helicopter, on a reconnaissance mission, had been due to land on the USS Wainwright by mid-afternoon Monday, Washington time.

Besides the ships, which searched through the night, the Navy sent several aircraft aloft Tuesday as part of the search for the helicopter. Iran's official Islamic Republic News Agency said that Iranian warships had brought down a U.S. helicopter.

Meanwhile, leaders of the Senate Armed Services Committee said that while they support Reagan's action, the United States should reassess its go-it-alone policy of protecting the vital sea lanes.

"This is an action that was taken that was justified, and, I think, measured," said Sen. Sam Nunn, D-Ga., the committee's chairman. "But I think we've got to make sure that we don't convert this into a U.S.-Iranian war."

Sen. John Warner of Virginia, the committee's ranking Republican, said "we'd like to see a more coordinated participation by our allies" in the gulf. "Our allies are there, but thus far they have declined efforts by our nation to suggest that we work in a more coordinated fashion."

Nunn and Warner were interviewed on NBC-TV's "Today" show.

Both Democrats and Republicans in Congress united Monday behind Reagan's warning that Iran will "pay a price" if it persists in trying to trade blows with a militarily superior force of American warships and aircraft in the Persian Gulf.

Nunn said Tuesday that "we need to re-examine our policy of protecting only 11 (Kuwaiti) ships. Many people don't realize it, but if a British ship or a French ship is attacked by an Iraqi aircraft right in the sight of our own American ship, we don't do anything. That has given the perception that we have lined up with the Iraqis."

"We've got to correct that perception and we've got to re-examine our policy," Nunn said. But the senator also said that "we need to get our allies . . . to protect certain zones."

House Minority Leader Robert Michel, R-Ill., appearing on ABC's "Good Morning America," said "I think we don't want to unilaterally be there, the policemen over there."

Rep. Robert Torricelli, D-N.J., a member of the House Foreign Affairs Committee, said on the same program that "we're not really protecting international shipping. What we're protecting is ships flying the American flag. Many of the criticisms that we had when this policy began is that we began it unilaterally without getting international cooperation."

"As time has gone on, the British, the French and the Italians have come to assume roles," he said. "But, indeed, if there was a mistake in the policy originally, . . . we did not act together and get cooperation when this began."

The initial platform attack had been in retaliation for the mine explosion last week that damaged the USS Samuel B. Roberts and injured 10 crewmen. White House spokesman Marlin Fitzwater said there is "conclusive evidence" that Iran planted the mine that exploded Friday.

"They must know that we will protect our ships, and if they threaten us, they'll pay a price," the president said in a speech to a business audience.

On Capitol Hill, Reagan won applause for consulting with Congress before sending the military into action.

"The mines have been clearly identified as manufactured by the Iranians and sown in the waters by the Iranians," said Senate Majority Leader Robert C. Byrd, D-W.Va. "The Irani are carrying out terrorist acts."

Defense Secretary Frank Carlucci said Iran's decision to fight back amounted to "foolhardy behavior."