Mitt Romney will name his vice presidential running mate on Saturday.

According to a statement the campaign released late Friday, the presumptive Republican nominee will announce his running mate at an 8:45am rally here on the USS Wisconsin--the first stop of his four-day bus tour of key battleground states. The campaign offered no further details, and aides traveling with Ronney declined to comment.

But Republican sources told NBC News, the Huffington Post, the Associated Press and CNN that Romney is expected to name Rep. Paul Ryan of Wisconsin--reports the campaign refused to confirm. In addition, ABC News's Jon Karl reported that former Minnesota Gov. Tim Pawlenty, Ohio Sen. Rob Portman and Florida Sen. Marco Rubio--all of whom were said to be on Romney's short list--have all been told they are not the pick.

Soon after the Romney campaign announced the Saturday appearance, speculation about the VP pick began, with Romney's choice of venue for the announcement offering a potential clue. The USS Wisconsin is the ship named after the home state of Ryan, the chairman of the House Budget Committee who has created buzz among conservatives recently. But the announcement also takes place in Virginia, whose governor, Bob McDonnell, has also been rumored as a possible vice presidential pick.

European news agencies consider Paul Ryan to be by far the best pick not for Romney, but for the US.