Defence Secretary Philip Hammond has warned he will resist further cuts to the armed forces in Chancellor George Osborne's forthcoming spending review.
After No 10 warned publicly last month that the military would not be immune from further financial retrenchment, Mr Hammond made clear that he would resist anything more than modest "efficiency savings".
In an interview with The Daily Telegraph, he said other Conservative Cabinet ministers believed that the greatest burden of any cuts should fall on the welfare budget.
There was, he said, a "body of opinion within Cabinet who believes that we have to look at the welfare budget again", and that "we should be seeing welfare spending falling" as a result of rising employment levels.
He said the "first priority" for the Government should be "defending the country and maintaining law and order" and that further defence cuts were not possible while meeting stated security objectives.
"I shall go into the spending review fighting the case for the defence budget on the basis that we have made very large cuts to defence, we've done that with the collaboration and co-operation of the military," he said.
"I am not going into the spending review offering any further reductions in personnel."
Mr Hammond's comments are likely to be welcomed by Tory backbenchers who have been calling for a return to a core Conservative values in the wake of the party's trouncing in the Eastleigh by-election.
However they will also heighten tensions within the coalition, with the Liberal Democrats resisting a further squeeze on welfare spending.
It was being made clear Mr Hammond's comments were aimed particularly at the Lib Dems following remarks by senior Lib Dem ministers indicating that they believed welfare spending should be protected over defence.
A Whitehall source said: "There is a real concern that the Lib Dems wants to protect the benefits culture at the expense of the armed forces".