U.S. authorities are seeking more than $3.5 billion from BNP Paribas SA to resolve federal and state investigations into the lender's dealings with sanctioned countries including Sudan and Iran, according to people familiar with the matter.

The agreement, which could come in the next month, is still being negotiated and the amount of the settlement could be higher than $3.5 billion, said four people who asked not to be named because the discussions are private. U.S. prosecutors are also seeking a guilty plea from BNP, the people said.

BNP said last month it may need more than the $1.1 billion it has set aside to settle the case. Julia Boyce, a BNP spokeswoman, declined to comment.

The BNP case marks a shift by U.S. prosecutors who are vowing not to give banks special treatment because of their size and influence on the economy. The Justice Department under Attorney General Eric Holder has been accused of letting banks off too easily following the worst financial crisis since the Great Depression.

BNP Paribas closed down less than 1 percent at 53.06 euros in Paris after falling as much as 2.3 percent on the news. The shares dropped 6.6 percent in 2014, while the 43-member Bloomberg Europe Banks and Financial Services Index gained 2.5 percent.

Prosecutors are pushing for BNP to plead guilty to criminal charges related to the conduct, a departure from previous sanctions cases which typically ended with deferred prosecution agreements that spared offending companies from pleading guilty. The bank and regulators are still discussing settlement terms, including the type of charges and whether the parent company or a subsidiary would plead guilty, one of the people said.

Manhattan U.S. Attorney Preet Bharara, Manhattan District Attorney Cyrus Vance Jr. and David O'Neil, the head of the Justice Department's criminal division in Washington, are working together on the BNP Paribas investigation. Benjamin Lawsky, superintendent of New York's Department of Financial Services, is also investigating the bank.

Peter Carr, a Justice Department spokesman, didn't immediately respond to phone and e-mail messages seeking comment. Spokespeople for Bharara, Vance and Lawsky declined to comment.

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