Nationalisation is still an option for troubled lender Northern Rock, and the government is not ruling anything out, Prime Minister Gordon Brown has said.
Savers' deposits at Northern Rock are guaranteed by the government
Mr Brown also rejected suggestions that he ignored warnings that the bank was in trouble and said everything possible was being done to secure its future.
He is facing calls to nationalise the stricken bank, which has an aid package from public funds estimated at £57bn.
But the prime minister said he still hoped for a sale to a private company.
On Tuesday, the Treasury expanded its guarantees on Northern Rock's liabilities, prompting talk that state ownership of the bank was a step closer.
It offered to cover any loss by financial institutions providing money to Northern Rock, hoping the move will restore confidence in the lender and let it offer normal services.
The Treasury had already guaranteed savers' deposits held at Northern Rock, after September saw the UK's first run on a bank in living memory.
"We are doing everything in our power to help Northern Rock find the right buyer for the future," the prime minister said.
"We do not rule anything out for the future."
Mr Brown said Northern Rock's collapse had been caused by an "unsound business plan".
But he said the fact that its problems had not spread to other institutions showed the "tripartite" regulatory system of the government, the Financial Services Authority and the Bank of England was "working well".
Mr Brown designed the system and implemented it in 1997.
The prime minister and Chancellor of the Exchequer Alistair Darling, who also attended the press conference, denied any rift with Bank of England Governor Mervyn King.
"The governor and I, and the chancellor, are completely at one in both the way we deal with these events and analyse what's happened," said Mr Brown.
Mr Brown also denied that he was hesitating over appointing Mr King for a second term as governor, adding that an announcement would be made in due course.
The chancellor said that "wide-ranging" reforms would be unveiled early next year to help prevent banks running into difficulties.
In a later interview with Channel 4 News, Mr Darling said it was "impossible" to calculate the size of taxpayers' exposure to Northern Rock since the guarantees offered by the government had not been called upon.
These guarantees were essential, Mr Darling argued, "to give the firm the breathing space it needs" to conclude a sale.
Two consortia, including one led by Virgin Group, are in talks about rescuing Northern Rock.
But there are real doubts as to whether either will be able to raise the money needed to pay off government loans because of the shaky state of financial markets.
Mr Darling also said the FSA would "learn lessons" from how it reacted to widely expressed doubts about Northern Rock's business this summer.
"It is clear that the FSA, having seen this problem, should have done something about it."