Prosecutors investigating the movement of money by global banks suspect HSBC of laundering money for Mexican drug cartels and moving cash for Saudi Arabian banks with ties to terrorists, according to federal authorities with direct knowledge of the investigations.


The federal and state prosecutors are also investigating whether HSBC flouted United States law by transferring money through its American subsidiary for sanctioned nations, including Iran, Sudan and North Korea.


The weight of the accusations could force HSBC, which has already set aside $700 million to cover the cost of potential fines, to pay at least $1 billion to settle the inquiry, said the authorities with knowledge of the investigation, which would make it the largest such settlement in history.


The money-laundering accusations against HSBC so far are more extensive than the potential violation of United States sanctions that is the focus of the investigations against other foreign banks, including Deutsche Bank and Commerzbank of Germany, BNP Paribas and Crédit Agricole of France and the Royal Bank of Scotland, said the law enforcement authorities, who requested anonymity because the investigations are continuing.


“This case is not about HSBC complicity in money laundering,” a spokesman for HSBC said in a statement on Friday. “Rather, it’s about lax compliance standards that fell short of regulators’ expectations and our expectations, and we are absolutely committed to remedying what went wrong and learning from it.”


The other banks either declined to comment or did not respond to requests for comment.


Anxious to resolve the investigation, HSBC reached out to federal prosecutors in July in hopes of securing a settlement by September, according to the law enforcement officials. But a settlement in the next couple of weeks is highly unlikely, the officials said. The Justice Department and the Manhattan district attorney’s office are poring over HSBC records and still need more time to gauge the full extent of the potential wrongdoing, according to the law enforcement officials. The Justice Department and the Manhattan district attorney’s office declined to comment.


HSBC was put in the spotlight in July when the Senate Permanent Subcommittee on Investigations said the bank “exposed the U.S. financial system to money laundering and terrorist financing risks” between 2001 and 2010. HSBC bank executives testifying at the hearing apologized for the bank’s past conduct and promised reform. On Friday, the bank said in its statement that it had “doubled global expenditure to significantly strengthen compliance as a control function.”


Pressure to resolve the investigation increased in the last month after Benjamin M. Lawsky, the superintendent of the New York Department of Financial Services, broke with federal and state prosecutors and moved against Standard Chartered, another British bank. He accused it of scheming for nearly a decade with Iran to hide from regulators 60,000 transactions worth $250 billion.


Adding to the desire for a speedy settlement, the authorities said, was rising antibank sentiment after recent scandals, including accusations that banks manipulated a crucial interest rate affecting the cost of trillions of dollars in mortgages and other loans.


To assuage prosecutors, HSBC officials have pointed out that they had strengthened controls to prevent money laundering and had replaced employees tainted by the accusations, according to the law enforcement officials. Further distinguishing HSBC from other banks under investigation, law enforcement officials said, was the complicity of senior bank officials. The Senate panel said in its report on HSBC that bank officials ignored warning signs and failed to stop illegal behavior at many points between 2001 and 2010.


An HSBC executive reportedly argued that the bank should resume its relationship with Al Rajhi Bank, a Saudi Arabian bank founded by an early supporter of Al Qaeda. Ultimately, HSBC’s American operations furnished the bank with at least $1 billion, according to the Senate report.