WASHINGTON » HSBC, the British banking giant, will pay $1.9 billion to settle a money-laundering probe by federal and state authorities in the United States, a law enforcement official said today.

The probe of the bank — Europe’s largest by market value — has focused on the transfer of billions of dollars on behalf of nations like Iran, which are under international sanctions, and the transfer of money through the U.S. financial system from Mexican drug cartels.

According to the official, HSBC will pay $1.25 billion in forfeiture and pay $655 million in civil penalties. The $1.25 billion figure is the largest forfeiture ever in a case involving a bank. Under what is known as a deferred prosecution agreement, the financial institution will be accused of violating the Bank Secrecy Act and the Trading With the Enemy Act.

The official spoke on condition of anonymity because the source was not authorized to speak about the matter on the record.

The London-based bank said it is cooperating with investigations but that those discussions are confidential.

The law enforcement official said an announcement of the agreement could come as early as Tuesday.

In regard to HSBC and Mexico, a U.S. Senate investigative committee reported that in 2007 and 2008 HSBC Mexico sent to the United States about $7 billion in cash. The committee report said that amount of cash indicated illegal drug proceeds.