"I'm sure this strike, which was a tactical and surgical success, has been a setback" for the Assad regime, Brennan said.
Nikki Haley, the USA ambassador to the United Nations, warned Syrian President Bashar al-Assad on Sunday that the US would launch new missile strikes against his regime if he carries out another chemical weapons attack. "We can't allow even the smallest use of chemical weapons".
Speaking at a briefing late Friday, U.S. Defense Secretary James Mattis and the Chairman of the U.S. Joint Chiefs of Staff General Joseph Dunford said the strikes will result in a long term degradation of the Assad regime's capability to develop and deploy chemical and biological weapons.
"We of course know our work in Syria is not done", Haley said.
"We are determined to completely crush ISIS and create the conditions that will prevent its return." she said, referring to the Islamic State extremist group.
The Syrian Armed Forces later said the US and its Western allies fired a total of one-hundred-and-ten missiles from manned aircraft and ships.
Trump had said: "Mission accomplished" on Twitter after the strikes, although U.S. Lt. Gen. Kenneth McKenzie at the Pentagon acknowledged elements of the program remained and he could not guarantee that Syria would be unable to conduct a chemical attack in the future. Responding to the airstrikes, Putin on Saturday condemned what he called "an attack on Syria".
"One again, just like a year ago when the United States attacked Shayrat Airbase in Syria, a staged chemical attack against civilians was used as a pretext, this time in Douma, a Damascus suburb".
The action was in response to a recent deadly attack in the town of Douma.
The Syrian Foreign Ministry Saturday condemned what it called "the brutal American-British-French aggression. which constitutes a flagrant violation of global law".
According to Vladimir Putin, the United States used a staged chemical attack against civilians to carry out a strike.
Russian Federation also decried the USA -led operation as a failure, saying the majority of the rockets fired at Syria were intercepted by the Syrian government's air defense systems.
New Western air strikes in Syria would provoke "chaos" in worldwide relations, Russian President Vladimir Putin told his Iranian counterpart, Hassan Rouhani, on Sunday.