The armed forces need additional funding this year if they are to maintain their current capabilities, Defence Secretary Gavin Williamson has warned.
Giving evidence to the Commons Defence Committee, Mr Williamson said "sacrifices" had already been made to other parts of the defence budget so the early phases of the Trident nuclear deterrent modernisation programme were properly funded.
He said more cash was now needed if the forces were to retain their existing capability levels ahead of the completion of the Modernising Defence Programme, launched last month, which is due to report in the summer.
"We will need more support," he said.
"We are going to have to have some discussions across government to make sure that over the coming year we have ability to ensure that we can deliver and keep those capabilities as they are until the Modernising Defence Programme has looked at it all."
He said they had already been forced to generate savings because, unlike in the past, the Treasury had not provided additional funding at the start of the programme to build the new Dreadnought submarines which will carry the Trident deterrent when the current Vanguard class is scrapped.
"We are all conscious of how important the development of the at-sea nuclear deterrent and the Dreadnought programme is and we have had to make sacrifices elsewhere in order to make sure the programme keeps going," he said.
"It is really important to get the profile correct of when the money actually flows into the system and when it is needed. At the moment it is not as we would wish it to be."
Lieutenant General Mark Poffley, the Deputy Chief of Defence Staff for Military Capability, warned the search for savings could have a detrimental effect on morale as it impacted on the quality of life of service personnel.
"It can go right the way down to the most trivial expenditure, car hire or the authorisation for telephones," he said.
"Those sorts of things make tiny little changes but at aggregate levels start to generate reasonable sums of money.
"It is absolutely the case that we need to be vigilant to the detrimental effect, particularly to service men and women's morale, when you are taking small incremental hits on what they perceive as their quality of life."
Mr Williamson said that the Government was committed to maintaining the overall size of the armed forces and meeting the Nato target to spend 2% of GDP on defence.
"Two percent is the floor. That is what the United States expects as an absolute bare minimum," he said.
"They can't be the ones expected to pick up the tab for our security in the North Atlantic and continental Europe."
Despite recent warnings by Theresa May and other senior figures of the threat posed by Russia, Mr Williamson said the Government wanted "sensible" relations with Moscow, but that their actions made it difficult.
"Russia is not a benign state," he said.
"We always hope to have a sensible relationship but we should not be blind to the challenges and threats that are growing from Russia.
"It becomes more complex to be able to work with Russia on a military-to-military basis when so much of what they do is to undermine our interests."