The US House of Representatives has approved a bill expanding background checks for all gun sales, including those at gun shows and on the internet.
The legislation is the most significant gun control measure to make progress in Congress in more than two decades.
The Democratic-controlled House passed it by 240 votes to 190. The bill is unlikely to be approved in the Senate, where Republicans have a majority.
President Donald Trump would also need to sign it for it to become law.
The White House said on Tuesday Mr Trump’s advisers would recommend that he veto the bill as it would apply “burdensome requirements” that were “incompatible with the Second Amendment’s guarantee of an individual right to keep arms”.
Critics of the legislation, including many Republicans, say the changes would not have stopped many of the recent mass shootings, including the one at a high school in Parkland, Florida, last year in which 17 people were killed, which sparked student-led activism for stronger restrictions.
Campaigners say there is strong public support for expanded checks and increasing dissatisfaction with congressional inaction.
