WASHINGTON - Central banks around the world on Wednesday announced steps to prevent a credit crunch among banks in Europe which are struggling with the region's debt crisis, boosting global share prices and the euro.

The US Federal Reserve, the European Central Bank and the central banks of Canada, Britain, Japan and Switzerland said in a surprise joint announcement they had agreed to lower the cost of existing dollar swap lines among other measures.

The swap lines are intended to ensure banks outside the United States have easy access to dollars, which have become more difficult for banks in Europe to obtain in the market as investor concerns about the euro zone debt crisis have grown.

The cost of the lines will be reduced by 50 basis points from Dec 5, the statement said.

Other new measures included setting up bilateral swap arrangements between the central banks so that any of them could provide liquidity in any of their currencies. The swap arrangements are good through Feb 1, 2013.

"The purpose of these actions is to ease strains in financial markets and thereby mitigate the effects of such strains on the supply of credit to households and businesses and so help foster economic activity," the central banks said.

But analysts said the measures were merely palliative, buying time for Europe to come up with more concrete measures to quell the crisis. If anything, the market's positive reaction was due in part to the expectation that this would be the first of other corrective steps taken by the ECB.

"This will not solve all deep-based funding problems which are due to the sovereign debt crisis," said Silvio Peruzzo, economist at RBS in London.

"But there is an issue with dollar liquidity, especially with foreign currency and this measure addresses that. This helps at the margin and also shows that central banks remain at unease with what certainly is very significant distress."

The actions on Wednesday, which included a decision by the ECB to lower the margin it requires European banks to put up for dollar loans, stole a page from coordinated efforts to battle the 2007-2009 financial crisis.

During that episode, the Fed set up dollar swaps with the ECB and the Swiss National Bank in December 2007. It increased those lines when Lehman Brothers collapsed in September 2008 and opened swaps with Japan, Canada and England in an effort to battle the most virulent stage of the crisis.

The facilities for the ECB, Japan, Britain and Switzerland are unlimited; swaps with Canada are capped at $30 billion.