J. Scott Applewhite, Associated Press
In this Jan. 7, 2015 file photo, House Ways and Means Committee Chairman Paul Ryan, R-Wis. is seen on Capitol Hill in Washington. Ryan says he will not run for president in 2016.

WASHINGTON — Republican Rep. Paul Ryan announced Monday that he will not run for president in 2016, instead focusing on building his resume in Congress.

Ryan, of Wisconsin, was the Republican candidate for vice president in 2012. There had been much speculation about his ambitions for 2016.

But with the start of the new Congress last week, Ryan became chairman of the powerful House Ways and Means Committee, which has jurisdiction over taxes, trade, Social Security and health care.

"After giving it a lot of thought, I've decided not to run for president," Ryan said in a statement. "Our work at the House Ways and Means Committee over the next few years will be crucial to moving America forward, and my job as chairman deserves undivided attention."

Ryan's announcement comes as his former running mate, Mitt Romney, is reaching out to former staff and supporters in key states, signaling interest in a third run for president.

Wisconsin Gov. Scott Walker has also expressed an interest in running for the Republican nomination, which could create competition for Ryan's support.

Ryan did not endorse any of his fellow Republicans Monday. He told NBC News it would be "premature."

Walker and Ryan grew up about 20 miles from each other in southeast Wisconsin. Both came of age in the 1980s during Ronald Reagan's presidency and both have established national followings among conservatives.

By all accounts Walker and Ryan have a close relationship. Ryan campaigned with Walker in the waning days of his successful re-election campaign last fall. And Walker has said they frequently exchange text messages.

Last week, Walker confirmed that he'd hired a national political adviser to lead his exploratory effort and vet possible staff. He said he's looking at creating a political action committee or other entity to raise and spend money.

Walker is scheduled to give a keynote speech Thursday at the annual winter meeting of the Republican National Committee in California. Later this month he and other potential GOP White House hopefuls are headed to a conservative summit in Iowa.

As for Ryan, running for president as a member of the House would be a daunting task. Only one sitting House member has ever been elected president — James A. Garfield in 1880.

Still, Ryan has a national following. He is a favorite among conservatives for developing detailed plans for reining in federal spending. Those plans, however, have made him a villain among many Democrats and liberal groups.

Just approaching his 45th birthday at the end of the month, Ryan has time to consider future presidential elections.

"It's clear our country needs a change in direction. And our party has a responsibility to offer a real alternative," Ryan said. "So I'm going to do what I can to lay out conservative solutions and to help our nominee lead us to victory."

"I want to thank everyone who encouraged me to run," Ryan continued. "Their words and continued support have been deeply humbling. And most of all I want to thank the people of Wisconsin for giving me the opportunity to serve our country."

Associated Press writer Scott Bauer contributed to this report from Madison, Wisconsin. Follow Stephen Ohlemacher on Twitter: http://twitter.com/stephenatap