FILE PHOTO: Chief of Staff to the Attorney General Matthew Whitaker attends a roundtable discussion with foreign liaison officers at the Justice Department in Washington, U.S., August 29, 2018. REUTERS/Allison Shelley/File Photo

SAN FRANCISCO (Reuters) - San Francisco’s city attorney on Monday questioned the recent appointment of a new acting attorney general, saying in a letter to the U.S. Department of Justice that his office may take court action if the DOJ does not provide a legal justification for the designation.

President Donald Trump last week named Matthew Whitaker to replace former Attorney General Jeff Sessions, who was forced out after months of attacks by Trump for recusing himself from an ongoing probe into Russian meddling in the 2016 presidential election.

The move made Whitaker supervisor of the investigation, which has hung over Trump’s presidency. Whitaker has criticized the probe in the past as too wide-ranging, which has raised concerns among Democrats that Sessions’ ouster and Whitaker’s appointment might be precursors to Trump moving to end it.

In the letter on Monday, San Francisco City Attorney Dennis Herrera said the city currently has four cases proceeding in court that name Sessions as a defendant. One of those cases led to an injunction blocking a Trump executive order over sanctuary cities.

Given that the Sessions resignation impacts those cases, Herrera said DOJ should provide legal justification for the Whitaker appointment. Otherwise, the city “may be forced” ask a judge for it, the letter said.

A Justice Department spokesperson could not immediately be reached for comment.

Sources told Reuters last week that Senate Democrats were considering suing Trump on the grounds that, in naming Whitaker, the president ignored a statutory line of succession at the Justice Department and deprived senators of their constitutional “advice and consent” role on some presidential appointments.

Herrera’s letter also questioned Whitaker’s appointment because he had not been confirmed by the U.S. Senate.