Updated 2:54 p.m. | President Donald Trump is prepared to again strike Syria if its president, Bashar Assad, launches another chemical weapons attack, a senior administration official said Saturday.

“If this act does not succeed, we will act again,” the senior official said, referring to Friday night’s cruise missile strikes on Syrian government targets.

Despite Trump declaring “Mission accomplished!” earlier in the day in a tweet, the official told reporters success would be defined by Assad not using chemical weapons again.

A perfectly executed strike last night. Thank you to France and the United Kingdom for their wisdom and the power of their fine Military. Could not have had a better result. Mission Accomplished! — Donald J. Trump (@realDonaldTrump) April 14, 2018

Senior administration officials said Saturday they believe the U.S.-French-British strikes, which were aimed at Assad’s chemical weapons infrastructure, hit their intended targets. But an opposition group on the ground there raised doubts as the sun rose in Syria.