The banks are being offered a pounds 150m debt-for-equity swap in return for pounds 80m of new cash. The deal could give them overall control of the group. Shareholders also have to approve the plan.
But there has been widespread speculation that a group of Japanese banks within the 28-bank syndicate is unwilling to participate.
WPP is seeking to reduce borrowings estimated at pounds 500m after being struck by a worldwide slump in advertising revenues.
But there have been reports of shareholder resistance to the proposed restructuring that has forced the company to rethink its plans to include an option to launch a listed subsidiary issuing pounds 150m preferred ordinary shares to banks or the issue of high- yielding subordinated loan stock.
Earlier this month Gary Klesch, the London-based American financier, announced that his company, Klesch and Company, had bought an unspecified amount of WPP's bank debt.
Mr Klesch would not say from which bank he had bought the debt. WPP said that it had not been advised that any debt had been consigned to another holder. But there have been signs for some time that some of the smaller banks in the syndicate are unhappy with their WPP loans and wish to withdraw from the syndicate.
WPP's shares were unchanged yesterday at 50p.