Former US Secretary of State Hillary Clinton backed President Barack Obama's attempts to seek military action against Syria and urged Congress to support him.
In a White House event about wildlife trafficking, Clinton diverted from the subject to comment on efforts to pressure Syria.
It would be an "important step" if the Syrian government of President Bashar al-Assad immediately ceded control of chemical weapons, she said.
"The Assad regime's inhumane use of weapons of mass destruction against innocent men, women and children violates a universal norm at the heart of our global order," Clinton said.
More top news
Mohanna Abdhou, known as Montana, was out with friends when two attackers cycled up to them and opened fire in Brent, north-west London.
The US president tweeted that Mrs May gave him "full details" of the incident during talks while he attended summits in Europe.
Police have raided another home in connection with the Manchester Arena attack as officers made a fresh arrest as part of the investigation.