Jeremy Corbyn is expected to grant Labour MPs a free vote on extending UK air strikes against so-called Islamic State into Syria, the BBC understands.
But the Labour leader is believed to want his party to take a position of opposition to military action.
Mr Corbyn has been meeting his shadow cabinet team, many of whom are likely to support air strikes.
It comes as David Cameron continues to try to build support for the extension of strikes from Iraq to Syria.
The prime minister has said he will only call a vote when he is confident of winning, and needs enough Labour MPs to back military intervention to make up for any Conservative rebels.
Ahead of the shadow cabinet meeting, Labour said 75% of party members it polled over the weekend had opposed bombing.
However the survey was called into question with one Labour MP calling it a “rather vague consultation”.
A free vote means Labour MPs would not be instructed to vote with the leadership. Mr Corbyn had previously suggested he wanted to agree a united position within his shadow cabinet and for Labour to approach the question “as a party”.
But he was warned of resignations from his front bench if he attempted to force his party to vote with him.
No date has been set for a Commons vote on air strikes – Defence Secretary Michael Fallon said the government was “continuing to build” its case.
Mr Corbyn has written to Mr Cameron requesting a two-day Commons debate to be held ahead of any vote.
A single day, the Labour leader said, “would inevitably lead to important contributions being curtailed”.