The United States has warned it is "prepared to do more" to stop the horrors that are taking place in Syria under Bashar Assad.
President Donald Trump unleashed a barrage of cruise missiles on a Syrian air base in retaliation for the regime's "barbaric" use of chemical weapons against its own people.
Nikki Haley, the US ambassador to the United Nations, told an emergency meeting of the world body's Security Council that Washington had taken "a very measured step" but was ready to go further.
She said: "We are prepared to do more. But we hope that will not be necessary.
"It is time for all civilised nations to stop the horrors that are taking place in Syria and demand a political solution."
Russia and Britain clashed at the tense round of UN talks in New York.
The UK's ambassador said President Assad had been "put on notice" and claimed Moscow had been left humiliated by its failure to bring him to heel.
But Russia accused Britain of "colonial hypocrisy" and "lies" as it warned against military involvement in Syria.
Russia's UN representative Vladimir Safronkov said: "Stop putting forward these unprofessional arguments and accusations against my country. These are not diplomatic. These are lies.
"Don't even try to get into fights in the Arab world. Nothing will work and nothing will be achieved.
"All Arab countries recall your colonial hypocrisy."
Russia has consistently denied that Syrian forces used chemical weapons, claiming the incident at Khan Sheikhoun was caused by a hit on a rebel chemical weapons plant, a claim dismissed by the West.
Matthew Rycroft, the UK's ambassador to the UN, said Russia has given Assad "everything he could have dreamed of" in its continued support.
He said: "The greatest war criminal of all, Bashar Assad, has now been put on notice.
"The US strike was a proportionate response to unspeakable acts that gave rise to overwhelming humanitarian distress."
"Russia sits here today humiliated by its failure to bring to heel a puppet dictator entirely propped up by Russia, Hezbollah and Iran," he added.
Russia accused the US of violating international law but Mr Trump said the dramatic strike from US warships in the Mediterranean was in the "vital national security interest".
Russian foreign minister Sergei Lavrov said the Americans had used a "far-fetched pretext" to justify the attack while the defence ministry in Moscow said it would be helping its Syrian ally strengthen its air defences.
Britain led international support for the attack, describing it as a "limited and appropriate" response to the use of chemical weapons by the regime of Assad against its own people.
Defence Secretary Sir Michael Fallon said the Government had been in "close contact" with the US administration in the run-up to the strike.
The Syrian military said at least seven people were killed and several others injured in the strike which caused extensive damage to the base at Shayrat, in central Syria, from where Tuesday's chemical strike was believed to have been launched.
Russian defence ministry spokesman Major General Igor Konashenkov sought to play down the impact, claiming fewer than half the missiles reached the air base, destroying just six Syrian MiG-23 fighters and leaving the runway intact.
The surprise barrage of 59 cruise missiles in the early hours of Friday, UK time, was the first time the US has struck directly against the Syrian government.
In an emotive broadcast, Mr Trump said he was responding to the regime's attack - believed to have involved sarin nerve agent - on the rebel-held town of Khan Sheikhoun which left at least 72 people dead, including 20 children.
"Using a deadly nerve agent, Assad choked out the lives of helpless men, women and children. It was a slow and brutal death for so many," he said.
"Even beautiful babies were cruelly murdered in this very barbaric attack. No child of God should ever suffer such horror."
Downing Street was swift to offer its backing for the US action, which was also supported by Israel, Australia, France, Germany and European Council president Donald Tusk.
A No 10 spokeswoman said: "The UK Government fully supports the US action, which we believe was an appropriate response to the barbaric chemical weapons attack launched by the Syrian regime, and is intended to deter further attacks."
In contrast, Labour leader Jeremy Corbyn condemned what he said was a "unilateral military action without legal authorisation or independent verification" which risked intensifying the Syrian conflict.
Mr Lavrov, on a visit to Uzbekistan, compared the US action to the invasion of Iraq by American and British forces in 2003.
"I want to emphasise that this is, of course, an act of aggression under a far-fetched pretext. Russia will draw conclusions from the actions of the United States in Syria," he said.