President Donald Trump
President Donald TrumpReuters

President Donald Trump on Saturday sent a letter to Congress in which he explained his reasoning for ordering a missile strike on Syria this week.

"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 in the letter, which was quoted by The Hill.

"The United States will take additional action, as necessary and appropriate, to further its important national interests," Trump added.

The letter was addressed to House Speaker Paul Ryan (R-WI.) and Sen. Orrin Hatch (R-UT), the Senate president pro tempore.

Under the War Powers Resolution, the president is required to submit an explanation for the use of force within 48 hours after military action is taken.

The deadline for Trump to do so would have been Saturday night.

Trump's letter echoed the comments he delivered an hour after the strikes on Thursday night, when he characterized the strikes as in the "vital national security interest" of the U.S.

“It is in this vital national security interest of the United States to prevent and deter the spread and use of deadly chemical weapons,” Trump said at the time.

A number of world leaders rallied around the American strikes on Friday, applauding the action as a necessary and proportional response to Syrian President Bashar Al-Assad’s alleged use of chemical weapons in the country’s Idlib province.

The Syrian government and Russia, a longtime backer of Assad, condemned the strike. A spokesman for Russian President Vladimir Putin on Friday called the strike an act of “aggression against a sovereign state” and accused the U.S. of violating international law.