WASHINGTON — With gun legislation taking shape on Capitol Hill, President Barack Obama has kept a low profile on an issue he has made a critical part of his second-term agenda.

The president has not been highly visible in the debate during the past three weeks as gun bills are being written. He's been embroiled in a budget battle that has dominated his time and for now is letting Vice President Joe Biden bang the drum for tighter firearms laws.

White House officials say the president plans to speak out on gun control as the issue moves toward a Senate vote in the coming weeks. But for now, he's staying out of delicate negotiations among lawmakers. The White House says he will become more vocal if the legislative process hits a roadblock.

Obama called for a gun control vote in his State of the Union address on Feb. 12 and followed up three days later with a speech on shooting violence in his murder-plagued hometown of Chicago. He's barely mentioned gun control publicly in the time since, other than during a minute of remarks Thursday, shortly after a Senate committee approved a bill to increase gun trafficking penalties.

Biden, a multi-decade veteran of negotiations over gun laws, has been more vocal in the White House's gun-control campaign with speeches, interviews and private negotiations.

Biden regularly meets with and calls his former Senate colleagues to talk about guns, including holding a White House meeting last week with Sen. Tom Coburn, R-Okla., in which they discussed negotiations on background checks that could win support from Republicans. He's even gotten involved at the state level by calling legislators in places like Colorado that are debating gun legislation.