One senior government source told the Financial Times they were “cautiously optimistic” that the number Labour MPs in favor of further airstrikes against the extremist group would be greater than the opposing Tory rebels.
A number of newly-appointed Labour shadow cabinet ministers have revealed their support for the measures, including shadow justice secretary Lord Falconer.
He told the BBC on Sunday if there was “a military and legal basis to doing it, then we should do it.”
However a Downing Street aid has recently said it is “not entirely clear we can win this,” and Prime Minister David Cameron has said he will not hold a vote on the matter unless he is sure of success.
The previous vote ended in embarrassment after defiant Tory MPs ensured the PM’s plans were thwarted.
Shadow Foreign Secretary Hilary Benn explained Labour’s current foreign policy debate, saying the party had not yet decided on an official stance.
He told the BBC on Sunday that “If the government has a proposition we need to look at what it is.”
He added that he did not believe Labour would support the withdrawal of the UK from the NATO alliance either, saying “I don’t think that is going to happen.”
Benn further distanced himself from party leader Jeremy Corbyn, by saying he believed the UK needed an “independent nuclear deterrent,” but insisted the official policy would be drawn up at the party conference which begins on Sunday.
Last week it was revealed by the defence secretary that UK airstrikes in Iraq had killed approximately 330 IS fighters.
Michael Fallon said the number was “highly approximate” and said the number included all strikes from September 2014 until the end of August 2015.
The deaths of British jihadists Reyaad Khan and Rahul Amin made headlines last month, when Cameron revealed they had been killed by an RAF drone strike in the IS stronghold of Raqqa, Syria.
Corbyn said the strikes were “legally questionable.”
Cameron is expected to hold a vote on further Syrian airstrikes as soon as November.