U.S. and European security officials have drafted a list of specific persons they want to apprehend for suspected involvement in the bombing of Pan Am Flight 103, as belief has hardened that Palestinian terrorists associated with a Damascus-based group were behind it, according to U.S. sources close to the investigation.

The sources said investigators also are fairly certain that they know the outlines or "trail" of the technical execution of the Dec. 21 bombing, which killed all 259 aboard and 11 on the ground in Lockerbie, Scotland.FBI Director William S. Sessions, in an interview on CNN's "Newsmaker Sunday" last weekend, said he was confident now that the investigation, involving U.S., British, West German and Scottish authorities, would be able to determine who was responsible for the bombing.

But neither he nor other FBI spokesmen have been willing to discuss details of the investigation. U.S. officials continue to caution that no final determinations have been reached. "They have names of suspects but no conclusions," one said.

Other sources said, however, that the FBI and European investigators are closer to reaching a conclusion than this statement suggested, and that they believe those involved were directly or indirectly associated with the Damascus-based Popular Front for the Liberation of Palestine-General Command (PFLP-GC), led by Ahmed Jibril.

It remains unclear whether the individuals were acting on behalf of Iran, Libya, Jibril or themselves, the sources said. Jibril has close ties to Iran and Libya, as well as to Syria, making it more difficult to determine on whose behalf his operatives may have been working.

Both Iran and Libya are known to hold grudges against the United States, Iran most recently because of the accidential shooting down of an Iranian Airbus by the USS Vincennes in the Persian Gulf last July, with all 290 passengers killed. Libya has vowed to revenge the U.S. air raids on Tripoli in April 1986 that nearly killed Libyan leader Moammar Gadhafi, as well as the U.S. downing of two Libyan fighter jets over the Mediterranean last January.

But Jibril has also made public threats to attack Israeli and American airlines. Fourteen of his operatives were arrested in West Germany last October in possession of plastic explosives and radio-cassette units similar to those used in the Pan Am bombing.

One indication of hardening U.S. suspicions about the involvement of Jibril operatives came on March 3, when two U.S. military attaches from the U.S. Embassy were caught with camera, binoculars and telephoto lenses outside a PFLP-GC training camp 25 miles outside Damascus.

Another indication has been the intensified dialogue between U.S. and Syrian officials about Jibril's terrorist activities, including a threat to execute the Indian-born British author of "The Satanic Verses," Salman Rushdie, at the behest of Iran's religious leader, Ayatollah Ruhollah Khomeini.

On March 6, the State Department called on Syrian President Hafez Assad to take "appropriate action" to ensure Jibril did not carry out the threat. In addition, U.S. officials have been pressing Assad for answers about what Jibril is up to and what controls Syria is exercising over him. But there has been no formal U.S. request yet that Syria expel him as in the 1987 case of another Palestinian terrorist leader, Abu Nidal, who is now based in Libya.