President Trump announced plans Tuesday to nominate Jessie K. Liu, the U.S. attorney for the District of Columbia, to become the Treasury Department’s undersecretary for terrorism and financial crimes, leading the administration’s aggressive use of economic sanctions as a national security and foreign policy tool.

If confirmed by the Senate, Liu, 46, would fill a vacancy created by the departure of Sigal P. Mandelker for a private-sector position. Over two years in office, Mandelker oversaw the administration’s stepped-up use of sanctions against Iran after the United States exited a landmark 2015 nuclear deal, as well as sanctions against Cuba, Venezuela and Russian entities and individuals.

Liu was confirmed in September 2017 as Trump’s nominee to become the District’s top law enforcement officer, leading the country’s largest U.S. attorney’s office and one that frequently handles politically sensitive investigations of the executive and legislative branches.

Liu came to the post after working on Trump’s transition team and serving as the Treasury Department’s deputy general counsel in 2017.

Earlier this year, Trump and Attorney General William P. Barr sought to promote Liu to the Justice Department’s No. 3 job — associate attorney general overseeing the department’s civil litigation. But she withdrew from consideration after Republican senators raised concerns about her past membership in a lawyers group that supported abortion rights and opposed the nomination of Samuel A. Alito Jr. to the Supreme Court.

As U.S. attorney for the District, Liu’s tenure overseeing 300 attorneys with unique jurisdiction to prosecute local and federal crimes overlapped with former special counsel Robert S. Mueller III’s investigation of Russian interference in the 2016 U.S. election. The office took over several Mueller prosecutions and referrals, including those of former Trump national security adviser Michael Flynn and political confidant Roger Stone.

The office stepped up sanctions-related investigations, issuing a warrant in August for the seizure of an Iranian tanker stopped by British authorities in Gibraltar, alleging that it was violating U.S. sanctions by transporting oil to Syria. It also won the first U.S. appeals court ruling to uphold heavy contempt fines against three large Chinese banks that refused to hand over customer financial records sought by U.S. prosecutors investigating possible North Korean sanctions violations.

Locally, Liu has scrambled with D.C. police to combat a spike in homicides, responding to back-to-back years of double-digit percentage increases in killings by prosecuting more defendants for gun and drug crimes in federal rather than local court.

However, some District officials and residents have criticized Liu’s office for issuing misleading data to oppose criminal justice reform and lobbying against expanding a D.C. law that would grant some inmates convicted of serious crimes a chance at early release.

Del. Eleanor Holmes Norton (D-D.C.) and D.C. Council judiciary committee chairman Charles Allen (D-Ward 6) have questioned why Liu’s office has seen declines in hate crime prosecutions since 2017, despite record numbers of arrests and complaints.

The office stumbled in some cases that critics say reflected the Trump administration’s efforts to punish the president’s perceived political enemies. A federal judge in October said the office’s apparent indecision over whether to charge former acting FBI director Andrew McCabe or to drop an investigation into whether he lied to investigators about an unauthorized media disclosure — after a grand jury apparently balked at approving an indictment — was undermining the credibility of the Justice Department.

Prosecutors earlier this year were forced to drop nearly 200 prosecutions after the mass arrest of protesters at Trump’s 2017 inauguration, a case launched before Liu took office. Civil liberties groups and defense lawyers said the cases were bungled and marred by overreach by law enforcement.

Liu, a graduate of Yale Law School, was an assistant U.S. attorney in the District from 2002 to 2006 before joining the Justice Department’s national security division and serving as a deputy assistant attorney general with the civil rights division until 2009.