Reports say the US says “all options are on the table” in response to a suspected chemical weapons attack in Syria, as Western leaders continue to weigh up military action.
White House spokeswoman Sarah Sanders told reporters that a final decision on military strikes had not been taken.
But she said the US holds Russia and Syria responsible for the incident.
The US National Security Council is to meet on Thursday, while UK PM Theresa May has called a cabinet meeting.
Activists, rescue workers and medics say dozens of people died in the rebel-held town of Douma on Saturday.
But President Bashar al-Assad’s government – which receives military backing from Russia – denies being behind any chemical attack.
“The president has a number of options at his disposal and a number remain on the table,” Ms Sanders said during a briefing on Wednesday evening.
“We haven’t laid out any specific actions we plan to take,” she added.
The comments appear to row back on President Donald Trump’s earlier warning to Russia that it should “get ready” for missile strikes in Syria.
“Get ready Russia, because they will be coming, nice and new and ‘smart!'” Mr Trump said in an early morning tweet on Wednesday.
He also called the Syrian leader a “gas killing animal”.