Mary Altaffer, Associated Press
Republican presidential candidate, former Massachusetts Gov. Mitt Romney, and his wife Ann wave at reporters as they arrive in Norfolk, Va., Friday, Aug. 10, 2012. Romney will announce his running mate Saturday morning Aug. 11, 2012 in Norfolk, Va., his campaign said Friday night.

WASHINGTON — Republican presidential hopeful Mitt Romney will announce his choice for his vice president at a campaign event in Norfolk, Va on Saturday, his campaign said.

NBC News reported an unnamed campaign source as saying the choice would be Rep. Paul Ryan of Wisconsin.

The announcement will be made aboard World War II-era battleship USS Wisconsin in Norfolk, Va., home to one of the country's largest naval bases, Saturday, Romney's campaign said.

Romney is starting a four-day tour through states considered to be key in the November election.

Ryan had been rumored to be among the top finalists along with former Minnesota Gov. Tim Pawlenty and Sen. Rob Portman of Ohio.

Ryan has taken on a prominent role as the top Republican on the House of Representatives' budget committee and is popular among the Republican Party's conservative base. He has advocated for deep spending cuts and is already experienced at facing down with President Barack Obama over economic issues.

Pawlenty has worked rallies and other events for Romney since ending his own short-lived presidential campaign. His popularity with conservatives as well as his working-class roots could prove a boost to Romney, who has been criticized as too moderate and also has to battle the perception that his wealth leaves him out touch with ordinary Americans.

Portman could help Romney win his own home state of Ohio, an important swing state with a reputation as a political bellwether. The Bush administration budget director is well-versed in economics and finance and has heavyweight foreign policy credentials owing to his work as a US trade representative and as a member of the Senate Armed Services Committee.

Analysts had also said Florida Sen. Marco Rubio and Louisiana Gov. Bobby Jindal were among the possible choices. Virginia Gov. Bob McDonnell's name has also been mentioned in the past, and he is due to appear with Romney Saturday.

The campaign launched an app for mobile phones last week that it claims it will use as its first official distribution channel for the vice presidential announcement.