The chief investigator probing the assassination of former Lebanese prime minister Rafik Hariri backed the creation of an international tribunal to prosecute the alleged perpetrators, saying without a court it is difficult to justify the investigation.

Belgian prosecutor Serge Brammertz told reporters Wednesday after briefing the Security Council on his latest report that a tribunal would be "the next logical step" because the Independent International Investigation Commission he heads is a fact-finding body — not a judicial institution that can issue indictments and conduct prosecutions.

Without a tribunal, he said, "it would be complicated or difficult to justify the existence of the commission."

• Visit FOXNews.com's Mideast Center for more in-depth coverage.

The establishment of a tribunal is being held up because the speaker of Lebanon's parliament, Nabih Berri, refuses to convene a session on the current crisis between the pro-government, anti-Syrian camp which wants a tribunal and the pro-Syrian, Hezbollah-led opposition which has demanded modifications to the proposal for the court.

The confrontation has stirred political and sectarian tensions that have threatened to tear Lebanon apart. The opposition demands the government give it a veto-wielding share of the Cabinet, but anti-Syrian Prime Minister Fuad Saniora has refused this, and is supported by the majority in parliament.

"Establishing a tribunal will be the logical next step after the investigation, or even in parallel to the investigation," Brammertz said, "since it's absolutely normal that at a certain moment in time it will be up to international prosecutors to look into the facts collected by the commission in order to see if there is enough evidence to prepare and indictment — and if not, to complete the investigation in this regard."

The commission already has thousands of documents, forensic evidence, analyses and hundreds of interviews to be handed over to a prosecutor, he said.

"It will be up to a tribunal later on to decide ... who has to be considered as responsible for this crime," Brammertz said.

He said the investigation into the killing of Hariri and 22 others in Beirut on Feb. 14, 2005 was making progress but will not be completed when the current mandate expires in June.

The Lebanese government sent a letter to Secretary-General Ban Ki-moon asking for a one-year extension for the Independent International Investigation Commission which Brammertz heads. France's U.N. Ambassador Jean-Marc de La Sabliere said he planned to introduce a Security Council resolution authorizing a one-year extension later this week.

Brammertz, who said he did not know whether he would be staying on after June, stressed that the commission will never mention any names of people allegedly involved in the plot publicly "because this will immediately have an impact on the right of defense."

He appeared at the council meeting with U.N. legal chief Nicolas Michel, who negotiated the agreement for the U.N.-backed tribunal with Saniora's government.

South Africa's U.N. Ambassador Dumisani Kumalo, the current Security Council president, said Brammertz came with Michel because one of the council members wanted to ask about the tribunal, which has no relation to the investigative commission.

"My understanding is that the parliament will eventually meet to deal on this question of the tribunal," Kumalo said, adding that he received the information in recent days from a Lebanese government delegation.

In his statement to the council, Brammertz reiterated that investigators have narrowed the possible motive for killing the wealthy tycoon to his political activities.

The chief investigator raised the possibility in a report to the council last week that the decision to kill Hariri was made before he embarked on a "rapprochement" with Syrian and Lebanese political figures.

The first U.N. chief investigator, Germany's Detlev Mehlis, said the killing's complexity suggested the Syrian and Lebanese intelligence services played a role in Hariri's assassination. Four Lebanese generals, top pro-Syrian security chiefs, have been under arrest for 16 months, accused of involvement in Hariri's murder.

Complete coverage is available in FOXNews.com's Mideast Center.