Giving his first reaction to the UN report on the former Lebanese prime minister's killing, Jumblatt also backed a call by Saad al-Hariri, Rafiq's son, for an international
court to try those responsible for the 14 February assassination.
"I advise the Syrian president to cooperate with the investigation in order to uncover the truth," Jumblatt said at his family home in Mukhtara, 19km southeast of Beirut.
The UN report, which was released on Thursday night, accused Syria of cooperating with its investigation only "to a limited degree" and said Syrian Foreign Minister Farouk al-Sharaa wrote a letter to the UN commission that contained false information.
Syrian officials rejected this on Saturday, saying their government had cooperated fully with the UN commission, and accused anti-Syrian witnesses of lying to the commission.
The report found that the bombing, which killed al-Hariri and 22 other people, could not have been carried out without the complicity of the Syrian and Lebanese intelligence services.
Jumblatt adopted a soft tone on Syria, telling reporters that the UN report contained "suspicions" not accusations, and said he rejected any international sanctions against the Syrian people.
A representative of the al-Mustaqbal (Future) party, Atif Majdalani, told Aljazeera that his party fully supported the holding of an international court in order to "protect the investigation and the truth behind this case".
"We are committed to know the truth. We will not bargain nor abandon the truth," he added.
Bashar al-Assad has been urged
to cooperate to get at the truth
Majdalani also said: "We believe that the Lebanese judicial authorities, which we trust, are now incapable of carrying out such an investigation and a fair trial."
He said the court should include Lebanese and foreign judges.
Commenting on the Hizb Allah movement's rejection of the idea of an international tribunal, Majdalani said: "We seek to achieve a genuine Lebanese reconciliation in all matters.
"Some members of al-Mustaqbal are holding current contacts with Hizb Allah and al-Amal party regarding this issue.
"Therefore, we can never take a step that threatens our national unity.
On the contrary, we seek to strengthen our national unity."
Majdalani said he had no details on the arrest of Mahmud Abd al-Al or the ban imposed on some high-ranking figures from travelling abroad.
Abd al-Al, a member of the pro-Syrian al-Ahbash Muslim group, was detained in Beirut early on Saturday on orders from Lebanese magistrate Elias Eid.
Rafiq al-Hariri (R) and 22 others
were killed in a bomb blast
"The international probe committee abides by confidentiality of investigation and names," he said.
"Mehlis's report has only revealed a clear part of a bigger entity."
He said there were many facts and names that had not been mentioned in the report.
"We are waiting for the results of the investigations, which will continue on 15 December and when more evidence and proof will be revealed," Majdalani said.
"I believe that matter of an international trial would not then be an internal problem," he added.