The interview, which was announced early on Sunday, comes just over a week after Al Hariri's shock resignation from Riyadh. Aoun refused to accept Hariri's resignation unless he tendered it in person in Lebanon.
Hariri's resignation has pitched Lebanon into a deep political crisis and shaken confidence in its heavily indebted state.
Lebanon has always been a hub for proxy battles between Saudi Arabia, Iran and other regional players.
In a television interview, the Saudi-allied Hariri held out the possibility he could yet rescind his resignation if Hezbollah agreed to stay out of regional conflicts such as Yemen, his first public comments since he read out his resignation on television from Riyadh eight days ago.
Saudi Arabia say it is trying to protect him from an assassination plot. "Everyone may not agree with Hariri's politics, but he is our prime minister".
Saudi Arabia has stepped up its rhetoric against Hezbollah and its patron, Iran, accusing both of supporting Shiite rebels in Yemen known as Houthis.
But Lebanese officials fear that during that meeting, Harari failed to take a hard enough stance against Hezbollah, the Shia Islamist group hated by Saudi Arabia - and included in Lebanon's coalition government.
"I am free", Mr Hariri told the TV interviewer.
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Riyadh subsequently accused Lebanon of declaring war on it because of Hezbollah.
"When Hariri's plane landed in Riyadh, he got the message immediately that something was wrong", a Hariri source told Reuters.
Prior to Hariri's interview, Aoun had also said that the restrictions on his freedom threw doubt on anything Hariri had said or would say, and that his statements could not be considered a statement of free will. Analysts said a more likely theatre for compromise would be Yemen, which Mr Hariri brought up a few times during his speech.
In Lebanon, political leaders from differing factions called on Hariri to return and address his political situation from Beirut.
"For there to be a political solution in Lebanon, it is necessary that all of the political leaders have total freedom of movement and that non-interference is a fundamental principle", Mr Le Drian said as he arrived for a meeting of European Union foreign ministers in Brussels.
Hariri had not been heard from since but met with foreign diplomats, and appeared with Saudi royalty and in Abu Dhabi.
His resignation was created to "cause a positive shock" in Lebanon, Hariri said, warning against what he said was Iranian interference that is ruining relations with other Arab countries.