UNITED NATIONS – In a move hailed by American officials as “dramatic,” and which has given hope to Syrian dissidents who aim to replace the Baath regime of Bashar Assad with a democracy, a U.N. investigator yesterday pointed to five former Lebanese security officials – all of whom have close ties to Syria – as possible suspects in the assassination of a former Lebanese prime minister, Rafik Hariri.

Mr. Assad, according to press reports from the region, is one of five Syrian officials that the U.N. investigator, Detlev Mehlis, has demanded to interview. The Syrian president is expected to arrive in New York in mid-September to attend a U.N. world summit. Continued non-cooperation by Syria with Mr. Mehlis’s team, as well as yesterday’s detention of the Lebanese suspects, are expected to have a huge effect on the Turtle Bay visit. Several diplomats predicted that Mr. Assad could be shunned by world leaders.

“We’re not going to meet with him,” America’s deputy ambassador to the United Nations, Anne Patterson, told The New York Sun.

At the request of Mr. Mehlis, the former Lebanese security officials were detained yesterday by Lebanese police and questioned at length by the U.N. investigation team. The team was sent to Lebanon by the U.N. Security Council that, under American and French leadership, ordered a probe into the February 14 Hariri murder. The bold assassination signaled the beginning of the political shift borne out of the pro-democracy movement known as the Cedar Revolution.

A former head of General Security, Jamil al-Sayyed, an ex-chief of police, Ali Hajj, and a one-time military intelligence chief, Raymond Azar, were detained and their homes were searched, a U.N. spokeswoman, Marie Okabe, said yesterday. Another suspect, a former commander of Lebanon’s Republican Guard, Mustafa Hamdan, met with interrogators later in the day. A fifth official, Nasser Kandil, a member of Parliament, was also named as a suspect in the assassination, Ms. Okabe said. Late last night, he returned to Lebanon from Syria and was interviewed by the Mehlis team. Mr. Mehlis is expected to hold a press conference in Beirut tomorrow.

“This is a very dramatic development,” Ms. Patterson said after the Security Council was briefed on the events by the U.N. undersecretary general for political affairs, Ibrahim Gambari. Investigators in Lebanon have arrested “four people in basically a very short amount of time, “which is “a credit to Mr. Mehlis, and his team, and to the U.N.,” she said. “These gentlemen who have been arrested,” Ms. Patterson added, “reportedly have long-standing ties with Syria.”

Ms. Patterson also told reporters that according to Mr. Gambari, and despite Syrian assurances to the contrary, Damascus still has not agreed to allow five Syrian officials to be interviewed by Mr. Mehlis. She said that a recent meeting in Geneva between Mr. Mehlis and Syrian officials failed to resolve the issue. “We’ll continue cooperating,” Syria’s U.N. ambassador, Fayssal Mekdad, said after Ms. Patterson spoke. “Full cooperation was pledged by the highest leadership in Syria.”

Syrian opposition figures were extremely encouraged by yesterday’s development. “If Syria does not cooperate with Mehlis in the next 10 days, Assad is going to be shunned in New York,” the president of the Washington-based, pro-democracy Reform Party of Syria, Farid Ghadry, told the Sun. The final Mehlis report on the Hariri assassination will have a “nuclear” effect on the Assad regime, he said.

“We know Maher Assad, the president’s brother, is involved in the assassination, as is Bashar Assad,” Mr. Ghadry added. He said that according to information his organization has gathered, Syrian officials were rebuffed when they tried to arrange meetings for Mr. Assad with Secretary of State Rice and several European officials during the U.N. summit.

In Lebanon, meanwhile, anti-Syrian politicians were said to be increasingly wary of possible Syrian retaliation. After several unresolved assassinations and terrorist explosion in pro-independence centers in Lebanon, the son of the late politician, Saad Hariri, and the Druze leader, Walid Jumblatt, were forced to leave the country. Reports of a Syrian “hit list” returned to the Lebanese press.

“To get to the bottom of this,” Mr. Ghadry said, referring to the Hariri investigation, “you need to assure those who fear Syrian retribution that there will be no Syrian retribution.”