Macron is not revealing his evidence, but reports say blood samples from some of the victims tested positive for a nerve agent and chlorine.
Defense Secretary James Mattis said a decision on a strike hasn't been made yet. Mattis stated he believes chemicals were used in the attack, but there needs to be actual evidence.
Thursday, President Trump said a decision would be made fairly soon. A much different tone from his previous statements, which sounded like an attack was imminent. The president and military leaders are weighing options to strike light or go heavy.
Experts said there are many factors to consider: there's also evidence Syria and its ally Russia are repositioning assets, warplanes, and naval ships in an attempt to prevent them being attacked possibly to prepare for a counter-strike.
In London, Prime Minister Teresa May has won cabinet approval for a military response.
May spoke to President Trump last night and they agreed to work closely.