The prime minister has summoned the cabinet to discuss the government’s response to the suspected chemical weapons attack in Syria.
Ministers will consider the options for backing military action threatened by the United States and its allies.
Theresa May is prepared to take action against the Assad regime in Syria without first seeking parliamentary consent, sources have told the BBC.
The allies want to prevent a repeat of an apparent chemical attack in Douma.
Mrs May has said “all the indications” are that the Syrian regime of president Bashar al-Assad, which denies mounting a chemical attack, was responsible.
If the cabinet approves UK involvement in military action, that would open the way for British forces to join an operation against Syrian targets that US President Donald Trump has said in a tweet “will be coming”.
During a briefing on Wednesday, however, White House spokeswoman Sarah Sanders appeared to row back on President Trump’s earlier warning to Russia that it should “get ready” for missile strikes against its ally.
She told reporters that the president had “a number of options at his disposal and a number remain on the table”, but added: “We haven’t laid out any specific actions we plan to take.”
Mrs May is reluctant to ask President Trump to hold off any action until she has the opportunity to consult MPs, the BBC understands from well-placed sources.
MPs are due to return to Westminster from the Easter recess on Monday.
Mrs May is still yet to unequivocally point the finger of blame at the Assad government but she has spoken of the need for action “if” the regime is found to bear responsibility.
BBC diplomatic correspondent James Landale said the cabinet was expected to back the PM, but she seems willing to act without the express support of Parliament.
However, he said this would anger some, including Labour leader Jeremy Corbyn, who believes Parliament should be consulted first.
Mr Corbyn has also warned that bombing could escalate the situation in Syria.
Mrs May has described the alleged use of chemical weapons as a “humanitarian catastrophe” that “cannot go unchallenged”.
She did not comment on Donald Trump’s tweet warning Russia to “get ready” for missiles being fired at its ally Syria.