WASHINGTON — The Justice Department on Tuesday sharply escalated economic pressure on Turkey by filing fraud and money-laundering charges against the country’s second-largest state-owned bank, accusing it of helping Iran evade United States sanctions.

The charges against the institution, Halkbank, came as the administration sought ways to project that it was taking a tough line with Turkey after President Trump effectively signaled this month that the United States would not stand in the way of Turkey’s desire to send forces into northern Syria.

Mr. Trump’s willingness to allow the military action has thrown the region into chaos and ignited an intense bipartisan backlash against him at home. As the criticism has mounted, the White House has emphasized the steps it is taking to restrain Turkey’s offensive, including a round of sanctions announced on Monday.

President Recep Tayyip Erdogan of Turkey had repeatedly raised the Halkbank case with Mr. Trump over the past year, urging the United States not to take further action, saying that to do so would unfairly expose Turkey to severe financial risks. One of the bank’s top executives was convicted on related charges last year, and the Justice Department has been reviewing since then whether to pursue the case further as Turkish officials and lawyers pressed the government not to indict the bank.