Five or six passengers from the hijacked TWA jetliner being held separately from the rest of the hostages are believed to be mostly U.S. military personnel and not, as has been publicly suggested, a group with "Jewish-sounding names," according to informed sources in Washington.

The sources said there is no direct confirmation of this, but several factors being analyzed here indicate that about four of those in the separately sequestered group were carrying U.S. military identification cards.

Indications here are that this smaller group -- as opposed to the larger group of 30 or so other passengers -- is being held by members of the same amorphous extremist Islamic faction, known loosely as Hezbollah, or Party of God, that engineered the initial hijacking last Friday.

They are being held separately, according to assessments here, because the extremist group that carried out the hijacking does not fully trust the leader of the more moderate and mainstream Amal Shiite militia in Lebanon, Nabih Berri, who is seeking to negotiate an arrangement with the United States and Israel in which all 40 Americans would be released in return for some 750 Lebanese Shiites being held prisoner in Israel.

There is also said to be some evidence that the identities of the original pair of Lebanese Shiite hijackers who took command of the jetliner shortly after take-off from Athens, and who murdered a U.S. Navy noncommissioned officer on board last Saturday, is now known to U.S. authorities.

The sources said that information reaching Washington also indicates that both hijackers, plus a third accomplice who never actually got onto the plane and was arrested in Athens, have relatives among the Lebanese Shiites being detained by Israel in the Atlit prison camp on the Israeli coast south of Haifa.

The principal demand of the hijackers is that Israel release these prisoners before the total of 40 Americans, including the three-man crew, that are still being held can be released.

Sources here said the other one or two passengers held in this small group are believed to be civilians but that they also do not appear to have Jewish-sounding names.

In effect, the smaller group are hostages within a larger hostage drama, but sources here said they would be included in any deal. Berri, who today acknowledged that it was the hijackers and not his militia that had control of these six or so passengers, has indicated they are safe.

The sources said that the hijackers apparently decided to take a chance on Berri's ability to arrange release of the Lebanese Shiites and in return, pledged that they would not harm the smaller group of hostages who were taken off the plane at the Beirut airport in the early morning darkness last Saturday.

The initial suggestion that several people with "Jewish-sounding names" were those that were whisked off the plane in the darkness of Saturday came last Sunday night when a freed TWA purser, Uli Derickson, told how she had refused to carry out hijacker demands that she go through passports and other identification gathered from the passengers and pick out "the passports of passengers with Jewish-sounding names." The assumption that those removed from the plane did have such names has persisted throughout the hijacking.

Informed sources say the persistence of these reports has been mostly in the press and that there was no corroborating information received through intelligence channels. As recently as Wednesday, however, White House national security adviser Robert C. McFarlane, when asked by reporters if it was the group with Jewish-sounding names that was removed from the plane, said "that's correct."

The State Department, however, on Tuesday said it had "no clear evidence" supporting such reports and Berri, in an interview today with CBS television, said "it is not true that they took them because they have Jewish names. This is not Jewish names. They are Americans like the others," he said.

At the funeral Wednesday of the slain Navy man, 23-year-old Robert Dean Stethem, Vice President George Bush said he was singled out for death "because he carried with pride among his papers the information that he was a member of the armed services of the United States."

In acknowledging that this smaller group of hostages is not under the control now of his Amal militia, Berri also told CBS: "They are under the control of the hijackers because maybe they don't trust me too well. But I have their word."

As viewed by some sources in Washington, Berri, the most influential of the Shiite leaders in Lebanon, must tread a thin line so as not to lose the mainstream support he has over the outcome of the hostage situation. The hijackers and the more radical, Iranian-influenced Shiites generally view Berri as too pro-western. Part of the hijack drama is not only an effort to get the Lebanese Shiites freed from Israel but also a longer-term struggle for power within Lebanon's Shiite population.

As one source here put it, the extremists appeared willing to relinguish some control over most of the passengers to Berri for the chance of obtaining the freedom of the Lebanese detainees but have kept the smaller group as "earnest money."