NEW CASTLE, Del. (Reuters) — President Joe Biden, weighing executive orders aimed at reducing gun violence following two mass shootings, said on Friday his administration is exploring whether he has the authority to take action on firearms made using 3D printers as well as on imported guns.

While Democratic-backed gun control legislation faces an uphill battle in the U.S. Congress because of Republican opposition, Biden could decide to take executive action in certain areas without the approval of lawmakers.

“We’re looking at what kind of authority I have relative to imported weapons – as well as whether or not I have the authority,” the Democratic president told reporters in Delaware.

Biden also mentioned “these new weapons that are being made by 3D equipment that aren’t registered as guns at all. There may be some latitude there as well.”

Often homemade, guns made using 3D printers have been a source of controversy. Some states have tried to limit the sales of blueprints that show users how to make them.

The president, a long-time advocate of gun control measures including increased background checks on gun buyers and banning assault-style weapons, has publicly committed to taking action following two mass shootings that killed a total of 18 people in Georgia and Colorado this month.

The White House has said it needs to review potential actions to ensure they have a solid basis in law and can survive an expected legal challenge.

“They have to go through a review process,” White House Press Secretary Jen Psaki told reporters.

Psaki said Biden would sign an executive order on guns but did not say when, adding, “We have to address this epidemic, address the threat of gun violence across many avenues. And he will. He’s committed to doing that.”

Biden on Tuesday urged the Senate to approve two bills passed by the Democratic-led House of Representatives on March 11 that would broaden background checks on gun buyers. Biden also called for a national ban on assault-style weapons. A previous ban expired in 2004.

Biden said on Thursday passing new gun control measures in Congress is “a matter of timing.”