The head of the Royal Navy has warned that the service needs another £1bn to meet future foreign policy demands.
Sir Jonathon said that the navy was "a very special asset"
Admiral Sir Jonathon Band appealed for the cash - a third of the navy's annual operating budget - to spend on new ships, at a journalists' briefing.
BBC defence correspondent Paul Wood said Sir Jonathon told reporters the navy "doesn't come for nothing".
Last year the Army's head, Gen Sir Richard Dannatt, claimed his troops were "at the limit of their capacity".
Paul Wood said Sir Jonathon had argued that Britain faced a choice between remaining as a first division sea-going nation or, as the officer put it, turning into Belgium.
With the government committed to an active foreign policy, the extra cash was essential to safeguard future capabilities and deliver an extra two aircraft carriers, he believed.
"The navy is a very special asset, and if you want to use it, it doesn't come for nothing," he told the journalists.
"We're at a scale now that requires a certain amount of investment to maintain.
"You can't do deterrence unless you are a really professional outfit."
Sir Jonathon also said that he had raised the issue privately with the prime minister and the chancellor.
He summarised his position to journalists by saying: "Give me two carriers and just less than a billion and I will be off your back, a happy boy."
He was not warning of an immediate collapse in the navy nor of any threat to the UK's ability to keep ships at sea.
During a speech in Plymouth in January, Prime Minister Tony Blair committed the forces to the fight against global terrorism and the alliance with the US.
The Ministry of Defence said the navy had been given 28 new ships in the past decade.
In a statement issued later through the MoD, Sir Jonathon insisted he was not criticising present funding levels but wanted to inform the debate about future funding of the armed forces.
"As the prime minister has said, if we as a nation are to extend what our armed forces can do, the public needs to feel comfortable with the economic choices needed to make that happen," he said.
Vice-Admiral John McAnally, former commandant of the Royal College of Defence Studies and president of the Royal Naval Association, said further cuts could challenge activities like intercepting drug traffickers in the Caribbean and guarding oil platforms in Iraq.
"Warfare has changed, warfare's always changing but navies have not become less important. The sea is a physical world wide web - 90% of everything that comes in or out of this country comes by sea."
Sir Jonathon is not the first senior officer to make an appeal for more resources to help meet the demands made of the services.
In December his predecessor, Admiral Sir Alan West, warned that equipment shortages could cost lives.
"I could see us in a position where we could have British servicemen's - that is navy, Army and air force - lives being lost because we have not made the sort of investments in things like the aircraft carrier."
And Army chief Sir Richard has also been keen to point out that worries over equipment shortages affect his service too.
In September 2006 he said his troops could "only just cope" with their commitments.