The letter was addressed to House Speaker Paul Ryan and Senate president pro tempore Orrin Hatch, Censor.NET reports citing the Hill.
"I acted in the vital national security and foreign policy interests of the United States, pursuant to my constitutional authority to conduct foreign relations and as Commander in Chief and Chief Executive," Trump wrote.
"The United States will take additional action, as necessary and appropriate, to further its important national interests," he added.
On April 7, U.S. warships launched 59 Tomahawk cruise missiles at a Syrian government airbase following a chemical airstrike in the province of Idlib blamed on President Assad.
UNICEF confirmed at least 27 children had been killed in the attack in Idlib.
The United States' Ambassador to the UN, Nikki Haley, said the response was "fully justified" and warned that the U.S. was prepared to do more but hoped that it would not come to that.
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