JPMorgan Chase was in talks on Sunday night for a deal that would quintuple its offer for Bear Stearns, the beleaguered investment bank, in an effort to pacify angry Bear shareholders, according to people involved in the negotiations.

The sweetened offer is intended to win over stockholders who vowed to fight the original fire-sale deal, struck only a week ago at the behest of the Federal Reserve and Treasury Department.

Under the terms being discussed, JPMorgan would pay $10 a share in stock for Bear, up from its initial offer of $2 a share  a figure that represented a mere one-fifteenth of Bear’s going market price.

The Fed, which must approve any new deal, was balking at the new offer price on Sunday night after several days of frantic, secret negotiations, these people said. As a result, it was still possible the renegotiated deal might be postponed or collapse entirely, said these people, who were granted anonymity because of their confidentiality agreements.