Tim Howard will make his debut

The Reds will play four matches in the ChampionsWorld Series Tour, as the club - and the sport of football - aims to raise its profile in the United States.

Celtic, Barcelona, AC Milan, Juventus, Boca Juniors and Mexico's Club America also take part in the seven-match series.

Sir Alex Ferguson's side flew to the United States on Saturday to prepare for their opening game against Celtic, which kicks off in the early hours of Wednesday morning (UK time).

US TOUR FIXTURES Man Utd v Celtic 23 July 0400 BST Celtic v Boca Juniors 26 July 0100 BST Juventus v Barcelona 27 July 2100 BST Man Utd v Club America 28 July 0000 BST Barcelona v AC Milan 31 July 0100 BST Man Utd v Juventus 1 August 0100 BST Man Utd v Barcelona 4 August 0100 BST

Football is still a minority sport in the USA, but following the success of the women's team, efforts are being made to boost its profile in the country.

The ChampionsWorld Tour will see the biggest array of talent playing on US soil since the 1994 World Cup.

There has been interest among football fans in the US, with United's games against Celtic in Seattle, Juventus in New Jersey and Barcelona in Philadelphia all sold out.

United's sale of David Beckham has undoubtedly reduced the potential media interest, but their signing of American goalkeeper Tim Howard will help.

A more fascinating aspect, however, could be the presence of United target Ronaldinho in the Barcelona side when the two teams meet in the final game of the tour on 4 August.

About 3,000 people turned out for United's first training session in Portland where they have set up a training base.

Former Sunderland striker David Bellion was the only new signing on board United's flight from Manchester Airport on Saturday, although goalkeeper Howard will join up with the squad this week.

Ferguson ordered United's other summer signing, Cameroon star Eric Djemba-Djemba, and French duo Fabien Barthez and Mikael Silvestre to stay behind following their involvement in the Confederations Cup.

Midfielder Juan Sebastian Veron was included in the travelling party despite recent speculation linking him with a possible transfer to Chelsea.

They will then go to Portugal before returning to England in preparation for the Charity Shield match against Arsenal in Cardiff on 10 August.

Man Utd squad in the USA: David Bellion, Nicky Butt, Roy Carroll, Rio Ferdinand, Darren Fletcher, Diego Forlan, Quinton Fortune, Gary Neville, Ryan Giggs, Roy Keane, Mark Lynch, John O'Shea, Phil Neville, Danny Pugh, Ricardo, Kieran Richardson, Paul Scholes, Ole Gunnar Solskjaer, Juan Sebastian Veron and Ruud van Nistelrooy.