His choice of words recalled a similar claim associated with President George W. Bush following the USA -led invasion of Iraq.
Defense officials from the countries involved in the attack gave differing accounts of how much warning was given to the Russians, Syria's powerful ally.
The Russian military had vowed to respond to any attack, and President Vladimir Putin's administration had repeatedly warned Trump was taking America down a unsafe path.
Strikes were aimed at "chemical weapons infrastructure" in what USA billed as a warning against Assad employing such weapons in future.
Opening the meeting, UN Secretary-General Antonio Guterres urged countries to uphold global law as the Security Council met to discuss military strikes carried out by the United States, France and Britain on Syria.
However, her Russian counterpart, Vassily Nebenzia, called on the Security Council to condemn the strikes.
China's foreign ministry said it objected to the use of force and warned that it could complicate the situation in Syria.
President Donald Trump responds to White House visitors as he makes his way to board Marine One on the South Lawn before departing the White House, Thursday, April 5, 2018 in Washington. "The United States of America will not allow the Assad regime to continue using chemical weapons". "Public estimates are as high as 200", she said.
That appeared to contradict Trump's own pledge that the United States, France and Britain would sustain the military campaign until Assad stops using prohibited chemical agents.
'Mission Accomplished' In Syria Strikes
North Atlantic Treaty Organisation representatives planned a special session to hear from US, British and French officials. Mattis said Friday there were no reports of USA losses in what he described as a heavy but carefully limited assault.
"A large part of its chemical arsenal has been destroyed", Le Drian told BFM television. It was not immediately clear whether Trump meant the allied military operation would extend beyond an initial nighttime round of missile strikes.
Trump said the United States would maintain pressure on Syria until the Assad regime suspends use of chemical weapons.
In the aftermath of the attack, the western powers set out their justification for military action that was carried out without a mandate from the United Nations and in the face of criticism from Assad's allies Russian Federation and Iran.
McKenzie says 105 weapons were launched against three targets in Syria.
They "are responsible for the regional consequences of this adventurist action", it said, condemning a "clear violation of worldwide rules and laws".
"A lack of accountability emboldens those who would use such weapons by providing them with the reassurance of impunity", he said.
"These are not the actions of a man", Trump said in televised remarks announcing the strikes.
Mr. Trump described a very specific type of target that the USA would go after, which are Syria's chemical weapon capabilities.
Secretary General Antonio Guterres urged member states to "show restraint in these risky circumstances and to avoid any acts that could escalate matters and worsen the suffering of the Syrian people". He says there also is no indication that Russian air defense systems were employed early Saturday in Syria.
"Such action could have risky consequences, threatening the security and stability of the region and giving terrorism another opportunity to expand after it was ousted from Iraq and forced into Syria to retreat to a large extent", it said.