The vice-presidential candidate will be named at an event on a former warship, the USS Wisconsin, in Norfolk, Virginia, at 09:00 EDT (13:00 GMT).

Unconfirmed US media reports say Mr Romney has decided on Wisconsin congressman Paul Ryan.

But the campaign has made no official comment on the candidate's identity.

Mr Romney is challenging President Barack Obama in the 6 November vote.

Analysts say Mr Romney will be hoping to wrest back momentum in the campaign after a series of pro-Obama campaign ads attacking his record.

The former governor of Massachusetts is set to begin a four-day bus tour through key battleground states.

The trip campaign will visit the states of Virginia, North Carolina and Florida before finishing in Ohio.

BBC