Federal regulators on Sunday night were pressing for the sale of yet another troubled bank  this time, the Wachovia Corporation  in a move that would concentrate power within the nation’s banking industry in the hands of a few giant lenders.

Wachovia, the nation’s fourth-largest bank, was negotiating to sell itself to Wells Fargo or Citigroup. Although the Federal Reserve and Treasury Department were pushing for a sale, the government was resisting pressure to provide financial guarantees to the buyer.

A sale to either Wells Fargo or Citigroup would further concentrate Americans’ bank deposits in the hands of just three banks: Bank of America, JPMorgan Chase and whichever bank acquired Wachovia would control more than 30 percent of the industry’s deposits.

Together, those three would be so large that they would dominate the industry, with unrivaled power to set prices for their loans and services. Given their size and reach, the institutions would probably come under greater scrutiny from federal regulators. Some small and midsize banks, already under pressure, might have little choice but to seek suitors.