A pre-trial judge confirmed the indictment of Hassan Habib Merhi who is "accused of being involved in the 14 February 2005 attack," the Special Tribunal for Lebanon (STL) said in a statement.
Four members of militant Shiite group Hezbollah are facing trial for the devastating suicide bombing that killed billionaire Hariri and 22 others on the Beirut seafront.
Hariri, from Lebanon's Sunni minority, was opposed to the Syrian occupation of Lebanon, while Shiite Hezbollah is closely linked to Damascus. The group adamantly denies responsibility for the attack.
Merhi, 47, the fifth wanted suspect in the case, is also a Hezbollah member according to Lebanese media.
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He is charged with coordinating the preparation and delivery of a video claiming false responsibility for the attack that was sent to pan-Arab satellite broadcaster Al-Jazeera with a view to protecting the real killers.
The indictment against him was confirmed by a judge at the Hague-based tribunal on July 31 this year, after a request by its chief prosecutor Norman Farrel earlier that month.
The STL issued warrants against the accused -- Mustafa Badreddine, 52, Salim Ayyash, 49, Hussein Oneissi, 39 and Assad Sabra, 36 -- in June 2011, and Interpol has issued a "red notice" for the suspects but none has been arrested so far.
Lebanese authorities were given a month to carry out a warrant issued on August 6 and report back.
On September 6, the Lebanese public prosecutor said that "so far the accused has not been found."
Hezbollah's leader Hassan Nasrallah has dismissed the tribunal as a US-Israeli conspiracy, vowing that none of the suspects will be arrested.