The two French officials also took up BNP's cause with Mr. Lawsky, who has the authority to revoke the bank's license to operate in the state, the Wall Street equivalent of the death penalty. In recent meetings, Mr. Lawsky suggested that he would not withdraw BNP's license but might temporarily suspend the bank from processing transactions through its New York branch on behalf of foreign clients, a process known as dollar clearing.
The United States investigation into BNP has centered on the bank's role, from 2002 to 2009, in processing transactions through its American operations for companies and countries that the United States government has hit with sanctions. Prosecutors suspect that BNP, aiming to flout those sanctions, purposely omitted the names of Sudanese clients from paperwork to transfer money so as to not sound alarm bells with bank employees in New York. In some transactions, according to the people briefed on the matter, BNP employees stripped away any information that could tie the payments to entities under sanctions.
Mr. Noyer recently remarked publicly that BNP's conduct "conformed with European and French rules, laws and regulations."
At the heart of the French government's campaign is the concern that American prosecutors have created a two-tiered system of justice: one in which American and British banks escape criminal charges and the other that forces BNP to plead guilty to sanctions violations and pay a record fine.
Hoping to whittle down the financial penalty — prosecutors and regulators initially sought about $10 billion — French officials have contrasted BNP's case with the fate of other big banks. The British bank HSBC, for example, paid $1.9 billion to settle money laundering and sanctions violations. Credit Suisse paid about $2.6 billion when it recently entered a guilty plea.
For BNP, a bank deemed too big to fail in France, the French officials warned that such a huge settlement could eat into the bank's capital, according to the people briefed on the matter. The bank's capital levels, the officials complained, could drop below an important threshold for financial strength.
One French official, speaking on the condition of anonymity, said that any discussions were intended to highlight the potential dangers to the financial industry as a whole, and were not meant as direct advocacy for BNP.
At first, the entreaties appeared to give American authorities some pause, the people briefed on the matter said. But when prosecutors discussed the bank's capital levels with American regulators, they concluded that the concerns were overblown.
BNP's concerns also lost some momentum after the Credit Suisse guilty plea. The Swiss bank's American chief executive, Brady Dougan, said the case would not cause "any material impact on our operational or business capabilities."
Now that a guilty plea is no longer seen as a death sentence for banks, the dollar-clearing suspension has emerged as the biggest threat to BNP, according to the people briefed on the matter. In the meetings last month with Mr. Lawsky, the French officials detailed the potential impact.
With BNP unable to handle any dollar-clearing in New York, clients could flee to competitors, the officials argued. The blow to the bank, the French officials warned, would only add to turmoil in the European financial system.