The patriarch, who heads Lebanese Maronite Christians, is scheduled to hold talks with King Salman, Crown Prince Mohammed bin Salman and Hariri.
"I wrote (my resignation) with my own hand", he said, rebuffing claims that he was being forced into resigning by Riyadh.
"But in a sense, his absence has been unifying".
Mr Hariri also suggested that he could rescind his resignation.
Lebanese President Michel Aoun (C) and Jordan's King Abdullah II (unseen) review the honor guard during an official welcome ceremony at Marka airport in Amman on February 14, 2017.
After two years of a devastating war, the Houthis still control much of Yemen's north while the south falls under the embattled President of Abed Rabbo Mansour Hadi, whose government is recognized by the international community and who is supported by the Saudi-led coalition.
However, Mr Hariri also held out the prospect that he might reconsider resigning if Hezbollah stopped intervening in neighbouring countries.
Hariri appeared for the first time in a television interview on Sunday, one week after quitting his post as premier. Organisers said more than 47,000 took part in the marathon.
"His remarks [made in the Sunday night televised interview] raised a ray of hope that he might return to Lebanon and help restore calm to the Arab country".
He said he decided to resign to save the country from imminent danger, but did not elaborate. The man, whose face was outside the frame, soon disappeared but not before the camera moved back to Hariri, who was staring toward him with an angry and disgusted look.
The Future TV channel had asked its viewers to share questions for Hariri under the hashtag #AskthePM in an attempt to dispel reports that the interview was pre-recorded.
The resulting power vacuum is regarded by Iran as an invitation to extend its tentacles across the Middle East. Its most effective proxy, nestled in Lebanon, is Hezbollah, a battle-hardened terror group that has threatened Sunni-run governments and the state of Israel.
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