Trump was hosting Qatari Emir Sheikh Tamim bin Hamad al-Thani to the White House for bilateral talks.
"We're making sure terrorism funding is stopped," Trump said about the U.S.' ties with Qatar. "We're working on unity in that part of the Middle East, and I think it's working out well. There's a lot of good things happening.
"He buys a lot of equipment from us – military things, airplanes, missiles, lots of different things," he added. "They've been great friends. We're working very well together. It's working out extremely well."
The emir touted "a very strong and solid" relationship between the two countries, noting that their "economic partnership includes $125 billion, and we want to double it in the coming years."
Al-Thani told reporters the region could not tolerate "a war criminal" like Syrian President Bashar Assad and he said the region cannot accept people who support terrorism.
The two leaders spoke as the U.S. prepares to respond to a suspected chemical weapons attack in Douma, Syria.
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Reuters contributed to this report