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.
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Most GCC monarchies accuse Tehran of meddling in their internal affairs and want Washington to be tougher with Iran, which secured a landmark nuclear deal with world powers when Trump's predecessor Barack Obama was in office.
They consider Tehran to be a destablising factor in the region.
US Secretary of State Rex Tillerson on Saturday 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."
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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."
Trump, accused of using anti-Muslim rhetoric on the election campaign trail, is later expected to tell Muslim leaders of his "hopes for a peaceful vision of Islam."
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