A high-ranking Hezbollah militant was among four people named in an indictment by the UN-backed tribunal investigating Mr Hariri’s assassination in 2005.
The Shiite group denies any role in the killing and has vowed never to turn over any of its members.
Druse leader Walid Jumblatt called for stability over justice. He pointed to widespread fears that the case could further divide the country, which has been recovering from decades of bloodshed, including a 15-year civil war that ended in 1990 and recent sectarian battles.
“As much as justice is important for the martyrs and the wounded, so too civil peace and stability is the hoped-for future,” he said at a news conference. “Civil peace is more important than anything else.”
Mr Jumblatt’s support is crucial if Lebanese authorities are to co-operate with prosecutors of the international court, which issued the indictments on Thursday.
One of the people named is Mustafa Badreddine, believed to have been Hezbollah’s deputy military commander.
He is the brother-in-law of the late Hezbollah military commander Imad Mughniyeh and is suspected of involvement in the 1983 bombings of the US and French embassies in Kuwait that killed five people.
Hezbollah’s leader, Sheik Hassan Nasrallah, has denounced the court as a conspiracy by the US and Israel and said last year that the group “will cut off the hand” of anyone who tries to arrest its members.