After a months-long search, Romney officially announced his choice of Ryan at an event on the retired battleship USS Wisconsin in Norfolk, Virginia on Saturday.

By a possible coincidence, Wisconsin is also Ryan's home state.

Ryan, 42, who is the House Budget Committee chairman, will join Romney in the struggle for the White House against Democratic President Barack Obama and Vice President Joe Biden. The election is scheduled for November 6.

Ryan's House-backed plans to lower taxes and slash federal spending have made him a favorite of the conservative Tea Party, a movement that is against taxes and in favor of limited government. The Tea Party played an important role in helping Republicans take over the House of Representatives in 2010.

Conservative pundits had openly urged Romney to pick Ryan because of his tough stance on taxes and government spending.

Obama slightly ahead

The Democrats, however, have sought to portray Ryan as somewhat of a bogey man, saying his budget plans will give tax breaks to millionaires and make damaging cuts in health programs for the elderly and poor.

The US election campaign has so far largely focused on the weak US economy.

Romney's choice of Ryan as running mate comes as surveys show the Republican candidate slightly behind Obama in the public favor.

He will be hoping to redress this imbalance on the bus tour he is starting on Saturday through the swing-states of Virginia, North Carolina, Florida and Ohio.

All four states were won by Obama in the 2008 elections, but are up for grabs once more.

Romney is to be formally confirmed as candidate at the Republican Party convention in Tampa, Florida, in a little over two weeks' time.

tj/jlw (Reuters, AFP)