In response, Fayssal Mekdad, Syria's UN ambassador told the UN Security Council his country had not hindered the investigation, led by Detlev Mehlis, a German prosecutor.
"We are ready to do whatever the commission requests us to do," Mekdad said on Tuesday. He said his Foreign Minister, Farouk al-Shara, welcomed a meeting with Mehlis.
The Syrian ambassador gave his government's first response to a 25-page report Mehlis delivered to the council on Monday.
He said his team had found new evidence implicating Syria in the truck bomb murder of al-Hariri and 22 others on 14 February 2005 in Beirut.
After the meeting, Mekdad told reporters: "We believe that this investigation will lead to the clearance of Syria because it is in our interest to find the truth.
"Syria has nothing do with this heinous crime."
Mehlis, who has headed the UN inquiry for seven months, said that cooperation with Damascus had improved, but he was not sure this would continue.
He said Syria agreed, after "much hesitation and procrastination" to let his team interview five suspects in Vienna last week.
Mehlis said: "At this rate the investigation might take another year or two. Cooperation in good faith should be diligent and timely.
"Syria has nothing do with this heinous crime"
Syria's UN ambassador
"It remains to be seen whether the Syrian cooperation will be in full and without any conditions."
Security Council members are expected to extend the investigation into al-Hariri's murder by another six months, as Lebanon and Mehlis want to possibly widen the inquiry to cover other assassinations, favoured by France.
But Mehlis will leave. He told the council he would return to Berlin after UN Secretary-General Kofi Annan names a successor. Annan said he expected to do this within two weeks.
The death of al-Hariri, an opponent of Syrian domination of his country, transformed Lebanon's political landscape. The killing led to a pullout of Syrian troops from Lebanon after three decades.
John Bolton, US ambassador, said Washington was still working out its response to sanctions, but called Syria's cooperation "grudging at best" and carried out at the "lowest common denominator to see what they can get away with."
He said: "Syria is not going to get away with obstructing this investigation and it is not going to get away with the consequences."
Bolton: Syria will not get away
with obstucting the investigation
Mehlis in his Monday report said he had 19 suspects, including the five questioned in Vienna last week. Two of them told him Syrian intelligence had burned documents, he said.
But Mekdad told reporters it was common when an army withdrew from one country to another that it burned papers, although he had no first-hand knowledge of this.
He said: "But I assure you these documents have no relevance to the investigation. Whatever information these people have on the investigation was given to the commission."