David Cameron will honour his commitment to above-inflation rises in the defence budget after 2015, senior sources have indicated.
Tensions have been growing in the Coalition as negotiations begin over how to save billions of pounds more in the 2015-16 spending review.
Defence Secretary Philip Hammond, who has already seen his budget slashed by 8% in real terms since 2010, is believed to be among ministers resisting further cuts.
Tory backbenchers are among those voicing fears that the long-term capabilities of the military could be degraded unless more money is found.
The issue has been cast into sharper relief by the Government's commitment of up to 330 personnel and air support to the campaign against rebels in Mali.
Protecting MoD budgets could mean harsher treatment for the police and other services.
However, it is understood the Prime Minister "does not resile" from comments he made in October 2010, when he appeared to accept that defence spending had to start rising again from 2015 onwards.