The chairman of the Joint Chiefs of Staff indicated yesterday that despite intensive efforts, the U.S. intelligence community has found no conclusive evidence to determine who is responsible for the terrorist bomb attack that killed more than 230 persons last month at the U.S. Marine headquarters in Beirut.

Gen. John W. Vessey Jr., appearing on "Meet the Press" (WRC, NBC), said that "several different outfits have claimed credit" for the bombing. "I really don't know who did it," Vessey said. "I wish I did."

Shortly after the Oct. 23 attack on Marine headquarters at the Beirut International Airport, President Reagan and senior administration officials strongly suggested that identification of the attackers was imminent.

"We have strong circumstantial evidence that the attack on the Marines was directed by terrorists who used the same method to destroy our embassy in Beirut," the president said in an address to the nation four days after the attack. "Those who directed this atrocity must be dealt justice. And they will be."

The embassy bombing last April killed 63 persons, including 17 Americans. Hizballah, a radical Moslem Shiite sect with ties to the Iranian leader, Ayatollah Ruhollah Khomeini, is suspected in that bombing.

The day before his speech, Reagan reportedly told a private meeting of Jewish Republicans that evidence indicated that "Iranian terrorists" were involved, along with Syrians.

The day after the speech, senior administration officials were quoted as saying that all of the intelligence gathered to that point suggested that "the Iranians" were responsible in the Oct. 23 attack on the Marine enclave.

Vessey's statement yesterday suggested no decisive progress since then, indicating the difficulty U.S. intelligence is having in pinpointing blame in what one senior administration official involved in intelligence operations has termed an extremely splintered network of terrorist groups.

The official said that he was not at all confident that the attackers could ever be identified definitively. Intelligence operations have been hampered significantly, he said, in the wake of disclosure in the media of U.S. monitoring of Iranian diplomatic cables which, until those reports, were a key source of intelligence information.

Precise identification of the attackers was central to discussion yesterday of possible U.S. retaliation.

Senate Majority Leader Howard H. Baker Jr. (R-Tenn.) said on "This Week With David Brinkley" (WJLA, ABC) that he would not rule out a retaliatory strike in the Middle East "if and when we can find out with precision and exactness" who carried out the attack.

Baker said the United States could not be expected to act as Israel did last week. Following a similar attack on an Israeli security headquarters in the port of Tyre that killed 60 persons, Israeli planes quickly raided Palestinian targets in central Lebanon, apparently not waiting to pinpoint blame.

"I have great respect for the Israelis. I even admire the way they respond promptly," Baker said. "I wonder how accurate their intelligence, their information may be about those who perpetrated the assault . . . ."

Appearing on the same show, Secretary of Defense Caspar W. Weinberger refused to discuss questions about the possibility of retaliatory or stepped-up U.S. military operations in the Middle East.

"I'm not going to deny it; I'm not going to affirm it; I'm not going to leave it open; I'm not going to leave it closed," Weinberger said. "I am just not going to discuss it."

Vessey said, "When American servicemen are killed and killed in any numbers, my gut reaction is to retaliate." But he said it would be "inappropriate" to say if any retaliation is being planned.

Vessey also said that he was assembling a panel of experts to advise the military on cooperation with the news media in the wake of complaints about the Pentagon's decision to prohibit news coverage of the first days of the Grenada invasion.

He said former Maj. Gen. Winant S. (Si) Sidle, a chief Defense Department spokesman during the Vietnam-war era, would head the commission, which also would include "experienced newsmen."