The US and its allies France and Britain launched air strikes, targeting sites associated with Syria's chemical weapons capabilities.
The joint operation was in response to a suspected chemical attack in the city of Douma last week.
President Donald Trump "enforces" the red line and the US will sustain the pressure on the war-torn nation, she said.
"With yesterday's military action, our message was crystal clear. The United States of America will not allow the Assad regime to continue to use chemical weapons.
"Last night, we obliterated the major research facility that it used to assemble weapons of mass murder," Haley told an emergency UN Security Council meeting on Syria here.
Haley said she had spoken to President Trump, who said if the Syrian regime uses "this poison gas" again, the United States is "locked and loaded".
"When our President draws a red line, our President enforces the red line," she said.
Haley said the US successfully hit the heart of Syria's chemical weapons enterprise, and because of these actions, it is confident that it has crippled Syria's chemical weapons programme.
"We are prepared to sustain this pressure, if the Syrian regime is foolish enough to test our will," Haley said.
"That failure is largely due to Russian obstruction. We call on Russia to take a hard look at the company it keeps, and live up to its responsibilities as a Permanent Member of the Council and defend the actual principles the United Nations was meant to promote," she said.
UN Secretary General Antonio Guterres told the Security Council that the airstrikes were reportedly limited to three military locations inside Syria.
Guterres said the Security Council has primary responsibility for the maintenance of international peace and security and called on the members of the Security Council to unite and exercise that responsibility.
"I urge all member states to show restraint in these dangerous circumstances and to avoid any acts that could escalate matters and worsen the suffering of the Syrian people," the UN Secretary General said.
Guterres emphasised that there is no military solution to the Syrian crisis and the solution must be "political".
Urging the Security Council to assume its responsibilities, Guterres said a "lack of accountability" emboldens those who would use such chemical weapons by providing them with the "reassurance of impunity".
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