VENICE, JUNE 11 -- President Reagan's comment at a news conference here today that "there could still be some lowering of the value" of the U.S. dollar set off frantic efforts by top aides to correct him and prevent a further drop by the dollar on international currency markets.

The president's remark at a poolside news conference prompted the most rapid correction of a Reagan statement in the 6 1/2 years of his administration. It came on a day when aides also were scurrying to correct or clarify other administration statements made by White House chief of staff Howard H. Baker Jr. or spokesman Marlin Fitzwater.

But aides were most disturbed by Reagan's contradiction of official administration policy on the dollar during a news conference in which he frequently groped for answers and seemed to find it difficult to finish his sentences.

Led by Treasury Secretary James A. Baker III, the administration in September 1985 launched a campaign to drive down the value of the dollar against other world currencies as a means of making the price of U.S. exports attractive and reducing the U.S. trade deficit.

But after a significant fall of the dollar Baker has contended since February of this year that any further decline would be "counterproductive." At the economic summit that concluded here yesterday, he and other U.S. officials said the goal of the administration is currency stability. They predicted that the value of the dollar would remain relatively unchanged.

Reagan said today, "Most of us believe that the dollar should remain stable." He then added, "It could be within reason that there could still be some lowering of the value in relation to other currencies."

Aides watched in consternation. As soon as the news conference ended, communications director Tom Griscom and Fitzwater buttonholed reporters milling around the pool of the Hotel Cipriani and insisted that administration estimates of the currency situation had not changed.

"The president's position is that he wants stability for the dollar," Fitzwater said.

Aides said they moved quickly to clarify what one of them called "an offhand comment" by Reagan because financial markets were opening in New York about the time the president finished his news conference. The dollar declined briefly on world markets after Reagan's statement but quickly recovered.

Some administration officials here were privately wondering whether the president could recover as quickly from a news conference performance that one White House aide acknowledged was "very disappointing."

Reagan's most difficult moment came when he was answering a question about the Soviet role in the Persian Gulf. He was asked whether he envisioned a coordinated role between the United States and the Soviet Union to keep the gulf open to navigation.

He tried to say that the United States needed Soviet support in the U.N. Security Council but couldn't remember the words "Security Council." After a long pause he said "committee" instead.

Whatever the word, Reagan's answer today left considerable confusion about the U.S. position on the Soviet role in the gulf.

After Howard Baker said in a television interview that the Soviets and the United States share a role as cotrustees of peace in the gulf, Secretary of State George P. Shultz and national security adviser Frank C. Carlucci emphasized that the administration opposes any Soviet role in the region.

Reagan appeared reluctant today to side with one key aide against another and chose a middle ground. Asked for the third time whether he endorsed a role for the Soviets as "coguarantors" of peace in the gulf, Reagan replied, "No, I've never thought of them that way at all, but I think it should be pointed out that they are also there because they have ships transiting that in commercial shipping, and this is what we're talking about."

Chief of staff Baker's comments have prompted many corrections as well. On ABC News today, he said he "accepted the Chinese government's statement" that it was not supplying Silkworm antiship missiles to Iran. But even before the taped interview was aired, a senior official circulated through the White House briefing room saying that Baker's statement was in error.

In another demonstration of administration confusion, Reagan disputed a statement made Wednesday by Fitzwater about the case of Mohammed Ali Hamadei, accused of playing a central role in the 1985 hijacking of a TWA plane and the murder of a Navy diver who was among the passengers.

Fitzwater said that Reagan had taken West German Chancellor Helmut Kohl aside at a dinner that was held Tuesday night and pressed him to extradite Hamadei to the United States.

The spokesman said Kohl had refused but left the impression Hamadei would be tried for murder in West Germany.

Reagan today said he had "not attempted to put any pressure" on Kohl, and the West German government said that no decision has been made on Hamadei's extradition. But when Reagan was asked directly if Fitzwater had been mistaken he said, "I do not know whether there's been a decision."