The mandate of the 20-month-old inquiry expires in June. The cabinet decided last week to ask for a one-year extension which, if approved by the United Nations, would come into effect from June 15.

“I don’t think that in four months they will have completed the job, that’s my appraisal,” Justice Minister Charles Rizk said in an interview on Saturday. “I think it’s a wise precaution to give the investigators as much time as they need without putting them under pressure.”

The Security Council has already extended the mandate of the inquiry twice following earlier requests from Lebanon. Rizk was asked if the commission, led by Belgian prosecutor Serge Brammertz, had said its inquiry would not be complete by June.

“Yes, I mean although I never interfere in the job of the commission,” he replied. “But my responsibility as minister of justice is to provide them with the environment necessary for them to do their job in a comfortable way which I thought I had to do.”

Lebanon has witnessed 15 attacks on politicians, journalists and public places since Hariri’s truck bomb assassination in central Beirut two years ago. A preliminary U.N. inquiry has since implicated Syrian and Lebanese security officials in Hariri’s killing. Syria denies involvement.

Brammertz praised Syrian cooperation with his investigation as “timely and efficient” in a December progress report to the Security Council. Detlev Mehlis, who led the early stages of the inquiry, had complained that Syria obstructed his work.

Four Lebanese ex-security generals have been arrested in connection with the crime. No indictments have been issued so far. Lebanon is working with the United Nations to set up an international tribunal to try suspects.

The anti-Syrian majority coalition accuses Syria of killing Hariri and says the opposition wants to block the tribunal to protect Syrian officials.

The opposition led by Syrian-backed Hezbollah and its allies says it agrees to the idea of the tribunal but wants to discuss its statute to ensure it is not used as a political tool.