Deutsche Bank, Credit Suisse and Citigroup are among the banks that will likely be added, said the sources, who requested anonymity because they were not authorized to speak publicly on the matter.

Last September, Facebook increased its credit line to $2.5 billion.

One of the sources said that the credit line may be increased to about $5 billion in the future.

In February 2011, Facebook set up a $1.5 billion credit agreement with affiliates of Morgan Stanley, JPMorgan Chase & Co, Goldman Sachs, Bank of America Merrill Lynch and Barclays Capital, the leading underwriters of the company's IPO.

Facebook plans to increase its credit line to help cover a tax bill related to employee stock awards that will vest soon after it goes public.

On February 1, Facebook filed regulatory documents for an IPO.

Bloomberg reported earlier on Friday that Facebook would add banks to its roster of IPO underwriters.

A spokesman for Facebook declined to comment. Representatives for Deutsche Bank, Citigroup and Credit Suisse also declined to comment.

(Reporting By Alistair Barr; Editing by Bernard Orr)

• A Permanent Economic Emergency