Manchester United yesterday joined forces with the New York Yankees in a marketing deal which will strengthen their bid for global domination, but the club insisted they will remain loyal to their roots.

The alliance will enable United to exploit the vast, untapped American market and sell their merchandise through the baseball giants' distribution network.

The other aspect of the deal, and which may prove to be of greater financial importance, is the clubs being able to sell broadcast and internet rights and sponsorship collectively.

That could be worth millions, if not billions, of pounds to United, and the immediate reaction saw a five per cent leap in the club's share price.

It led one City analyst to predict that the Premiership champions were now likely to lead a drive to form a breakaway superleague. But Peter Kenyon, United's chief executive, insisted that was not on the club's agenda.

Kenyon, in New York for the announcement, said: ''We are committed to the Premier League and domestic English football.''

The marketing partnership is being seen as a long-term strategy, so there will be no immediate influx of money for manager Sir Alex Ferguson to spend on new signings or new deals for current players.

Kenyon added: ''It is not a financial deal today, it is an alliance between the greatest sporting franchises in the world.

''YankeesNet are not going to pick up our wage bill I wish they would! This is an off-the-field relationship.

''A lot of the issues we both face concern media rights and sponsorship, and that is an area that is very exciting.

''We have been looking long and hard at how we develop our international supporter base and North America was always an important market for us.''

The company that owns the Yankees, YankeeNets, also controls the NBA's New Jersey Nets and ice hockey side the New Jersey Devils. They will use United's own network in Europe and the Far East to sell their distinctive merchandise.

The teams will share market information, develop sponsorship and joint promotional programs and sell each other's licensed goods.

The deal is another step towards the day when United will be able to broadcast their matches over the internet, with fans all over the world paying a fee to log on and watch the game.

It will be several years before that becomes a possibility. High-speed internet access will need to be available to all and sundry, and that scenario is predicted as being at least five years off.

Kenyon added: ''We are looking to technology to deliver more content to more of our supporters in more countries.

''We have been working on not just the live aspect of this but packaging fairly unique products which our supporters want and delivering it to them in the right media.

''In the new world of digital distribution and the internet there are a whole host of things we can work on.''

United have agreed a 13-year sponsorship deal worth £302.9m with Nike, to start in August, but Kenyon said there was no conflict with their Yankees agreement.

YankeeNets chairman Dr Harvey Schiller believes the US market is ripe for picking by United. He said: ''Pretty well every young person in the United States plays soccer.''

Under the deal, David Beckham and Fabien Barthez will be paraded at the Yankee Stadium, with Yankees' El Duque and outfielder Bernie Williams visiting Old Trafford.

The two clubs will swap information on player training, fitness and health, and United will have a pre-season tour of North America in 2003.

Kenyon sees many similarities between United and the Yankees.

United, worth a staggering £1bn, are already the richest football club in the world with revenue that dwarfs the rest of the Premiership and major European clubs like Barcelona, Real Madrid and Juventus.

They are chasing their seventh Premiership title in nine years.

The Yankees are the wealthiest baseball team in the United States, worth around £400m. They have won three of the last four titles the World Series and, in all, a record 26.

United director Sir Bobby Charlton also travelled to New York for the announcement.

He said: ''This is to make friends and grow the sport. We are not in the process of selling our souls to another sport.''

Coincidentally, Ipswich chairman David Sheepshanks is also in the States looking at the possibility of a similar tie-up with his club to the deal which United have agreed.

Sheepshanks is visiting basketball, baseball and American football clubs, studying their marketing operations and discussing a possible tie-up between Ipswich and one of the clubs.

l Manchester United have pipped Real Madrid as the most popular club among European fans, according to a survey. United were number one among 15 per cent of the fans, followed by Real Madrid (14%) in the survey conducted by a German marketing company