evidently with Italian consent -- to free four hijackers of the cruise ship Achille Lauro this week underscores how widely different the responses to terrorism have become between the United States and its closest Arab and European allies.

Since the hijacking last June of a TWA plane by Shiite terrorists who held 39 Americans hostage for 17 days, the United States has sought tighter international coordination and common tactics in combating terrorism.

That goal, however, has been thwarted by fundamentally different viewpoints on this issue, as well as rifts over Middle East policies in general and the Palestine Liberation Organization specifically.

While the United States on principle refuses to negotiate with terrorists or grant concessions, most of its European and Arab allies are clearly willing to do both -- at least under some circumstances -- as the latest incident illustrates.

At the heart of the difference, according to European diplomats, is the European tendency to view terrorism as a "political" problem that has to be coped with at least partly in political terms, while the United States tends to regard it as an "apolitical" phenomenon that must be uncompromisingly confronted either in legal or military terms.

European diplomats say this difference reflects Western Europe's experience of terrorism as primarily an internal problem, while for the United States it has been largely external, involving attacks on American interests and citizens abroad.

The French strategy has been particularly frustrating for the U.S. officials promoting international cooperation against terrorism, since Paris has told Washington it prefers "a bilateral approach" because it is "more efficient and more discreet," according to a European diplomat. Among U.S. antiterrorist specialists, this Gallic attitude is known as "the French factor."

"It's worrying," Israeli Foreign Minister Yitzhak Shamir said during a luncheon yesterday with editors and reporters of The Washington Post. "The European countries are distancing themselves from the United States . . . and not only in this problem.

"It's very difficult without the cooperation of the European countries to achieve something of this kind," he said referring to international cooperation against terrorism.

Equally worrying to administration officials is the frequent selection of American citizens -- particularly if they are Jewish or military personnel -- for special harassment or even killing by Middle East terrorists. In the TWA hijacking and this week's piracy, the only fatalities were American.

This vendetta appears to stem from a perception among Arabs and Iranians -- particularly among Islamic fundamentalist terrorists -- that the United States is not evenhanded in its Middle East policy and is the main political and military supporter of their chief foes, Israel and the late shah of Iran.

The Achille Lauro incident was yet another example of the chasm separating Israel and the United States on one side of the terrorism issue from European and moderate Arabs on the other side.

Egyptian and Italian authorities said they guaranteed the terrorists safe passage from Egypt in the belief that no passengers had been harmed. It was unclear last night, in the midst of rampant confusion over the terrorists' whereabouts, whether that guarantee had been honored.

Egypt denied negotiating with the terrorists. But it appears that Cairo made a concession in agreeing to immunity and safe passage.

Italian Foreign Minister Giulio Andreotti explained the Italian position Wednesday in these terms: "The way of negotiations is not the way of the weak, but the way that is constructive."

The only condition the terrorists had advanced for their surrender, Andreotti said, was to get off the Italian cruise liner first and "probably to be able to have some favorable treatment."

Both Egyptian and Italian leaders emphasized, however, that their lenient attitude toward the terrorists would not have prevailed had they known about the murder of the American hostage, Leon Klinghoffer.

Had he known, Andreotti said, "it would have been illicit to say, 'Let's have an amnesty.' "

The difference between the U.S. and Italian attitudes toward dealing with the Middle East generally and its terrorists in particular is underscored by the widely varying attitudes toward the Palestine Liberation Organization, which Israel insists is behind much of the current upsurge in terrorism.

The Italians have deliberately sought to cultivate ties with the PLO. Italian Prime Minister Bettino Craxi has met with its chief, Yasser Arafat.

The United States, by contrast, refuses to deal with the PLO politically until it recognizes Israel.

As one administration official put it, "The Italians thought they could do a deal with their PLO buddies."

Ironically, despite all the tough talk from Washington and apparent differences in approaches in dealing with terrorism and terrorists, the U.S. record has often been inconsistent with the principles espoused by the Reagan administration. In at least one incident, France took a far stronger measure of retaliation than anything the United States has done to date.

After the bombing by Shiite terrorists of the French and U.S. military barracks in Beirut in October 1983, it was the French alone who struck back with an air raid on a Shiite headquarters in eastern Lebanon.

By contrast, neither during nor after the TWA hijacking in Beirut did the administration retaliate for the event or the killing of the American passenger.