Manchester United will be joined on their pre-season tour of the United States by six other European clubs, organisers say.

Premier league rivals Chelsea and Liverpool, Scottish premier league Celtic, Italian Serie A clubs AC Milan and AS Roma and German giants Bayern Munich make up the Champions World series.

United, who four months ago committed to return to the U.S. following a successful tour last July and August, will play three matches in north America this July.

They meet Bayern in Chicago on July 25, Celtic in Philadelphia on July 28 and current European Cup holders Milan at Giants Stadium, New Jersey, on July 31.

Chelsea play three matches in total, against Celtic in Seattle, Roma in Pittsburgh and Milan in Philadelphia.

Liverpool will meet Celtic in East Hartford, Connecticut, while Roma also face Liverpool at Giants stadium and Celtic in Toronto, Canada.

Seven venues will be used in all, with capacities ranging from 40,000 at Rentschler Field, East Hartford to 80,242 at Giants stadium.