The Commerce Department began a 90-day pause in an October order to assess the "risk of firearms being diverted to entities or activities that promote regional instability, violate human rights, or fuel criminal activities."

The pause, which includes shotguns and optical sights, ends on Thursday. The Commerce Department could decide to make the halt on export licenses permanent, return to previous practices, or impose other permanent restrictions.

The letter, which was signed by Warren and Senator Richard Durbin as well as U.S. Representatives Joaquin Castro and Norma Torres was sent to Commerce Secretary Gina Raimondo. It voiced support for returning export authority oversight to the Department of State from Commerce - something which changed under then-President Donald Trump's tenure.

In addition, the lawmakers asked Commerce to extend its review, declare publicly that it intends to curb exports, commit to better post-shipment oversight, and shorten the period export licenses are valid from four years to one year.

(Reporting by Mike Stone in Washington; editing by Jonathan Oatis)

By Mike Stone