Getting a foothold in neighboring countries is a way for Iran to exert influence.
He resigned in early November in a strange television announcement from Saudi Arabia.
A 64-year-old man in custody of U.S. Immigration and Customs Enforcement died Saturday at an Aurora hospital, the agency said Monday
A recent attack on an Egyptian mosque played a prominent role in the meeting.
Hariri previously announced he would resign on Nov. 4 while he was in Riyadh, Saudi Arabia.
He said he will resign again on Wednesday, during Lebanon's Independence Day celebrations.
President Donald Trump made the announcement during a Cabinet meeting at the White House, saying the declaration "should have happened years ago."
Hariri was in Saudi Arabia for two weeks, leading to speculation he wasn't allowed to leave.
Hariri has been in Riyadh since his resigned as Lebanon's prime minister, leading some to suspect Saudi Arabia called on him to step down.
Almost a week after his surprise resignation, Lebanon's former prime minister still hasn't returned from Saudi Arabia.
The two prominent Islamic countries are locked in a Cold War-like struggle for regional dominance.
Saad al-Hariri claims Iran and Hezbollah are interfering with Arab world affairs.