The United States will keep up the pressure on Syria after its intense overnight wave of missile strikes, despite the prospect of escalating Russian ill-will that could further inflame one of the world's most vexing conflicts.
Standing firm, the Trump administration on Friday signalled new sanctions would soon follow the missile attack and the Pentagon was even probing whether Russia itself was involved in the chemical weapons assault that compelled President Donald Trump to action.
The attack against a Syrian air base was the first US assault against the government of President Bashar Assad.
Much of the international community rallied behind Mr Trump's decision to fire the cruise missiles in reaction to this week's chemical weapons attack that killed dozens of men, women and children in Syria.
- Syria strikes 'unforgivable act of aggression' - N Korea
- Alt-right turns on Trump over Syria strikes
But a spokesman for Russian President Vladimir Putin warned that the strikes dealt "a significant blow" to relations between Moscow and Washington.
At the United Nations, Russia's Deputy Ambassador, Vladimir Safronkov, strongly criticised what he called the US "flagrant violation of international law and an act of aggression" whose "consequences for regional and international security could be extremely serious".
He called the Assad government a main force against terrorism and said it deserved the presumption of innocence in the chemical weapons attack.
US officials blame Moscow for propping up Mr Assad.
"The world is waiting for the Russian government to act responsibly in Syria," Nikki Haley, the US ambassador to the UN, said during an emergency Security Council session.
"The world is waiting for Russia to reconsider its misplaced alliance with Bashar Assad."
Ms Haley said the US was prepared to take further action in Syria but hoped it wouldn't be necessary.
The official Saudi Press Agency reported that King Salman complimented Mr Trump in a telephone conversation for his "courageous decision".
Saudi Arabia, one of the most vehement opponents of Mr Assad, said the missile barrage was the right response to "the crimes of this regime to its people in light of the failure of the international community to stop it".
In Florida with the president, Treasury Secretary Steven Mnuchin said additional economic sanctions on Syria were being prepared.
Thursday night's strikes - some 60 cruise missiles fired from two ships in the Mediterranean - were the culmination of a rapid, three-day transformation for Mr Trump, who has long opposed deeper US involvement in Syria's civil war.
Advisers said he was outraged by heartbreaking images of young children who were among the dozens killed in the chemical attack.
The decision undercut another campaign promise for Mr Trump: his pledge to try to warm relations with Moscow.
After months of allegations of ties between his election campaign and the Kremlin - the subject of current congressional and FBI investigations - Mr Trump has found himself clashing with Mr Putin.
On Friday, senior US military officials were looking more closely at possible Russian involvement in the poison attack.
Officials said a drone belonging to either Russia or Syria was seen hovering over the site after the assault. The drone returned late in the day as citizens were going to a nearby hospital for treatment. Shortly after, officials say the hospital was targeted.