Le Drian will arrive in Saudi Arabia on Wednesday and meet with powerful Crown Prince Mohammed bin Salman in the capital Riyadh before holding talks with Hariri on Thursday, the aide told a foreign ministry briefing.
As it was unclear when Hariri will leave Saudi Arabia to return home, the timing of the meeting "may be adjusted", the aide said.
Lebanese President Michel Aoun on Wednesday accused Saudi Arabia of having "detained" Hariri, who announced his resignation in a surprise statement from the kingdom on November 4.
"Nothing justifies the failure of Prime Minister Saad Hariri to return for 12 days, therefore we consider him to be held and detained, contrary to the Vienna Convention," Aoun said in a tweet on the official Lebanese presidency account.
Hariri, who has long been close to Saudi authorities, insisted in an interview with his party's television channel over the weekend that he had freedom of movement and would return to Lebanon in the coming days.