US President George W Bush has defended a rescue package to tackle the worst financial markets crisis for decades.

The cost to taxpayers from shoring up markets was better than the alternative of job losses and blighted retirement accounts, he said in a radio address.

The US Treasury is proposing a fund worth up to $800bn (£440bn) to buy back a large proportion of the bad debt in the US mortgage market.

The fund would hold the debts until they can be sold off in the future.

Mr Bush said the measures required the US "to put a significant amount of taxpayer dollars on the line".

"But I'm convinced that this bold approach will cost American families far less than the alternative," he said.

"Further stress on our financial markets would cause massive job losses, devastate retirement accounts, further erode housing values, and dry up new loans for homes, cars and college tuitions."

'Queasy' Congress

Congressional and Treasury officials will meet later to work on the plan.

Talks will continue throughout the weekend and the package is expected to be signed into law within days.

Share prices rallied after days of turmoil

It is believed the intention is to find a way of bringing all the bad debts into one organisation whose task will be to hold them on behalf of the taxpayer until they can be sold off at some point in the distant future, says the BBC's Justin Webb in Washington.

There are some members of Congress who are queasy at the thought of the taxpayer taking on hundreds of billions of dollars of currently worthless debt, he says.

But the leader of the Democrats in the House of Representatives, Steney Hoyer, said he expected quick action.

After a week of turmoil, stock markets around the world rallied on news of the rescue plan, with the UK's FTSE 100 closing on Friday with its biggest one-day gain.

'Maximum impact'

Earlier, Mr Bush said swift, politically bipartisan action was needed to keep the US economy from grinding to a halt as problems sparked by the credit crisis had begun to spread through the entire financial system - leaving jobs, pensions and companies under threat.

"These are risks the US cannot afford to take. We must act now to protect economic health from serious risk," he added.

PESTON'S PICKS For us here in the UK the big question is whether what Paulson's proposing makes it more or less likely that our government will have to launch a similar rescue scheme for our banks

Treasury Secretary Henry Paulson said a "bold" move was needed to restore the financial system's health.

Giving few details, Mr Paulson said the Bush administration was stepping in with a plan to remove so-called "toxic debts" from US banks' balance sheets.

The programme, he said, must be "large enough to have maximum impact".

In the meantime, he said that the government would be stepping up action to increase the availability of capital for new home loans.

Once this difficult period was over, Mr Paulson said, the government's next task would be to overhaul bank regulations.

The chairman of the Senate Banking Committee, Christopher Dodd, said he and his colleagues would need to see the details of the plan first, but he accepted that quick action would be needed.

"We understand the gravity of the moment," said the Democratic senator.

Rescue moves

Earlier on Friday, the government announced plans to guarantee US money market funds - mutual funds that typically invest in low-risk credit such as government bonds and are often used by pension funds - up to a value of $50bn, in a move to further restore confidence.

The Treasury and the Fed have finally realised the depth and systemic nature of the crisis John Ryding, economist

Meanwhile, the Securities and Exchange Commission temporarily banned "short-selling" in the stocks of 799 companies. Short-selling is a form of trading which effectively bets that the value of a company's shares will fall.

"The Treasury and the Fed have finally realised the depth and systemic nature of the crisis," said John Ryding, an economist at RDQ Economics

"We believe that these actions will constitute the wider firebreak that will contain the crisis."

Mounting fears that the credit crisis is beginning to spread out through the financial system have rocked shares and companies recently.

Investment giant Lehman Brothers collapsed this week, rival Merrill Lynch was bought out by Bank of America, and the US government has bailed out insurer AIG with an $85bn rescue package and state-backed mortgage lenders Fannie Mae and Freddie Mac.