A wide-ranging discussion is under way in the Reagan administration on the risks, benefits and timing of reprisal against international terrorism, and informed officials said yesterday that the president now believes military force should be a component of the response.

These officials said that many options are being considered, including the bombing of terrorist training sites. Military officials were said to have pinpointed prospective targets, using up-to-date photographs considered improvements over any the administration has possessed in the past.

"There can be no effective long-term strategy that doesn't include a willingess to use force," a senior administration official said. "The key requirement for that strategy, however, is that the use of that force be in keeping with American values and that it be effective in achieving what you want to do."

The discussion now occurring in the administration is reminiscent of the debate late in 1983 after the suicide bombing of a Marine Corps headquarters in Beirut that cost the lives of 241 U.S. servicemen. The bombing and the subsequent withdrawal of U.S. forces from Lebanon triggered an inconclusive struggle in the administration in which Secretary of State George P. Shultz and national security affairs adviser Robert C. McFarlane argued for reprisals and Defense Secretary Caspar W. Weinberger and the Joint Chiefs of Staff stressed the risks of retaliation.

An official said yesterday that, while the lines of debate remain basically the same, there is now "a crucial difference" in the way the issue is being discussed.

"The difference now is that everyone recognizes we're going to have to hit back at the terrorists," the official said. "The questions are how do it at just the right time, with the greatest effectiveness and in a way that has the fullest possible support of world opinion."

A senior administration official said that effective use of force against a center of terrorist activity could deter future acts of terrorism in the Middle East. He acknowledged that some high-ranking military officials contend that a U.S. strike could encourage reprisals against U.S. military bases but said that the hijacking of TWA Flight 847 last month and the killing of a Navy diver aboard the plane demonstrate that Americans are already at risk.

"The possibility of further acts of terrorism exists independently of any action the United States might take, but putting terrorists on notice that they face risks will diminish the number of incidents against our citizens over time," the official said.

The previous debate on terrorism led to a decision in late 1984, a year after the withdrawal from Lebanon, to approve a covert operation directing the Central Intelligence Agency to train and support counterterrorist units. Four months later foreign members of one of the units, acting without CIA knowledge or authorization, launched a car bombing in Beirut that killed 80 persons but missed the radical Moslem leader who was the apparent target.

In the wake of this incident, President Reagan and the CIA canceled the program of support for the counterterrorists.

In effect, the administration is now restarting the debate about what to do about terrorism under circumstances in which Syria has become a paramount influence in Lebanon.

Reagan's speech denouncing international terrorism Monday omitted mention of Syria, and a senior official reiterated yesterday that the administration is still "hopeful" that the Syrians will bring pressure to free seven Americans who have been kidnaped in Lebanon during the past 16 months and are believed held by Shiite extremists.

In his Monday speech Reagan linked Iran, Libya, North Korea, Cuba and Nicaragua as members of an internationalist terrorist confederation with ties to the Palestine Liberation Organization and other terrorist groups. An official said that Reagan was trying "to develop a base of public support for action" and that he would continue to make terrorism a major theme because it "will be on our agenda publicly for a long time."

The words of the speech, proposed by McFarlane and written largely by speechwriter Anthony Dolan, were controversial in the administration. Some officials said the language Reagan used was "overdone," and they cited in particular the phrase in which the president described the terrorist nations as "run by the strangest collection of misfits, looney tunes and squalid criminals since the advent of the Third Reich."

Officials said that what is emerging from the discussion is a criterion for antiterrorist action that would require that any U.S. strike be "surgical" and clearly tied to a terrorist act. Ideally, officials would like to take military action on the verge of a strike against a U.S. target or just after an attack. They also said that the U.S. activity would require an after-the-fact justification that could be supported by aerial photographs.