"The commission will also seek to interview [former Syrian Vice-President] Abd al-Halim Khaddam as soon as possible," the spokesperson said, referring to the man who said in a TV interview broadcast on Friday that Bashar al-Assad, the Syrian president, had threatened Rafiq al-Hariri, former Lebanese prime minister, months before he was assassinated in a 14 February bombing.
The commission - whose mandate was recently renewed by the UN Security Council for another six months - has reported that several people whom al-Hariri spoke to after he met al-Assad in August 2004 said the Syrian leader had threatened al-Hariri over Syrian plans to extend the term of Lebanon's president.
Syrian officials such as the foreign minister, Farouq al-Sharaa, have denied that any threat was made.
"The UN commission has already sent a request to interview Syrian President Bashar al-Assad and Foreign Minister Farouq al-Sharaa, among others," the spokesperson said.
"The commission is waiting for a response from the Syrians," the spokesperson added.
The spokesperson declined to say when the request to interview al-Assad was made.
Large anti-Syria protests broke
out after al-Hariri's murder
In two interim reports published late last year, the commission accused Syrian and Lebanese intelligence officials of being involved in the killing of al-Hariri. In an interview with the media, the outgoing commission chairman, Detlev Mehlis, has said the Syrian authorities were behind the assassination.
Syria has denied the charge and has tried to discredit those who testified to the commission.
The assassination of al-Hariri, in a blast that killed 22 others in central Beirut, was a turning point in modern Lebanese history. He was seen as a quiet opponent of Syrian influence in Lebanon, and his killing provoked mass demonstrations for and against Syria.
Syrian forces that entered Lebanon in 1976 at the request of Arab countries left the country in 2005.
Lebanese anti-Syria politicians claim the Syrian military presence had turned their country into a Syrian colony.
Pro-Syria Lebanese say the Syrian military presence had a key role in ending the 15-year Lebanese civil war and maintaining law and order afterwards. They prefer the anti-Syrian sentiment in Lebanon to foreign pressure.
Numair Ghanim, head of the foreign affairs committee in the Syrian People's Council, told Aljazeera that the Syrian officials were hearing UN's demands from the media.
"Unfortunately, we still receive the decisions of the international committee probing al-Hariri's assassination through media organisations," Ghanim said.
"This harms the secrecy and the procedures of the investigation," he added.
"Syria has not yet received the committee's demand officially," he said.
"When is it officially directed to the Syrian government, the decision will be studied by jurists at the Syrian Foreign Ministry," he added.
A pro-Syria protester's banner
reads: No to intervention
Ghanim expressed hope the committee's decision to interview al-Asad and al-Shara did not come as a result of Khaddam's statements, released a few days ago to the al-Arabiya satellite channel.
"Khaddam's speech was based on false and fragile basis and was full of contradictions," he said.
"The Syrian policy is a clear one that sticks to its national and regional rules and rights.
"No one is allowed to harm these rights," he said.
On the other hand, Amin Gemayel, Christian leader and former Lebanese president, described Khaddam's statements as "mostly credible" in an interview aired by Aljazeera on Monday.
Germayel, though, held Khaddam responsible for what he called "Lebanon's security disasters".