Merrill Lynch is believed to be in talks with Bloomberg over the sale of the bank's 20 per cent stake in the news service-to-trading data group.

The bank has held the stake for two decades, and it is believed to be worth as much as $6 billion. The bank is thought to have begun discussions over the sale of its holding with Bloomberg, which has the right of first refusal in the event of any disposal.

Bloomberg was founded by and remains in the control of Michael Bloomberg, the Mayor of New York.

It is not known how advanced are the talks between the two companies, but it is believed that Merrill may help the media group to finance the re-purchase of its stake.

Wall Street banks have been seeking to sell assets to plug their balance sheets with cash or similarly liquid securities. Their rush for cash has emerged after the finance groups were forced to write down billion of dollars worth of assets which became worthless after the credit crisis that erupted last year.

Citigroup has already warned investors that it may sell up to $500 billion worth of assets over the next two to three years.

Should Merrill Lynch succeed in selling its Bloomberg stake, the price it received would provide a key valuation on the private media company, which has always been secretive about its profitability.

Bloomberg is 72 per cent owned by Mr Bloomberg, whose precise wealth has never been disclosed.

Some analysts on Wall Street have estimated that his company could be worth $20-30 billion and that it has annual operating profits of about $1.5 billion.

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