The meeting on the second day of Trump's visit to Saudi Arabia, part of his first foreign tour since taking office, came hours before the US president is scheduled to address an Arab Islamic American Summit.
Leaders of the Gulf Cooperation Council posed for a photo with Trump before they walked into their meeting.
The GCC groups Saudi Arabia, Bahrain, Kuwait, Oman, Qatar and the United Arab Emirates, all of which are traditional allies of Washington.
They consider Tehran to be a destablising factor in the region.
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US Secretary of State Rex Tillerson yesterday demonstrated a tougher position on Tehran, saying multi- billion-dollar defence deals signed with Riyadh aim to protect Saudi Arabia from a "malign Iranian influence."
In a joint press conference with his Saudi counterpart Adel al-Jubeir, Tillerson urged newly re-elected Iranian President Hassan Rouhani to dismantle his country's "network of terrorism" and end "ballistic missile testing."