Updated

By Simon Evans

HOUSTON (Reuters) - Major League Soccer is aiming to break into the American sports mainstream with a series of high-profile signings as the league looks beyond the "Beckham effect" and seeks to capture the enthusiasm generated by the World Cup.

Media reports have suggested that Mexico captain Rafael Marquez and AC Milan's Brazilian forward Ronaldinho could copy former Barcelona striker Thierry Henry and move to the MLS.

It is not yet a return to the 1970s when the North American Soccer League brought in Pele, Franz Beckenbauer and Johann Cruyff, but New York's acquisition of Henry, as well as the league's new push, mark a higher level of ambition.

"I think we are prepared to make the next step as a league and we know we need to improve our quality and our visibility and our owners are stepping up and improving the product," LA Galaxy coach Bruce Arena, the former U.S. national team coach, told Reuters.

"I think Henry is a fabulous addition to the league and I think that other quality players that still have good football left in them are going to come to MLS and that is just the start -- I think we are going to continue to attract some quality players."

Behind the scenes, MLS clubs have been working hard to try to bring in more "designated players" -- top-paid performers whose salaries mostly do not count against the league's stringent salary cap.

Reports say that LA Galaxy, who have the league's best known foreign player in England's David Beckham, have been trying to persuade Ronaldinho to leave Milan for California. Arena was unwilling to comment.

In a further indication of the kind of moves MLS is looking to make, league commissioner Don Garber confirmed this week that MLS sides had tried to bring in Real Madrid's record goalscorer Raul before his switch to German club Schalke.

In April, MLS changed its rules to allow teams up to three players under the "Beckham rule." That, allied with the boom in interest in the game due to the success of the World Cup on television, has led to the desire to attract big-name talent.

DIFFERENT THINGS

Garber told Reuters that clubs were looking for different things from their imports.

"In one market it might all be about garnering massive amounts of attention to break through the clutter because it is a very competitive marketplace," he said.

"In other markets it might be about having a player who fits in within their community, in others about a player that can really help them be competitive on the field. The fact that rule is flexible is one of the beauties of our system."

Although Marquez, as a defensive player, might not capture the imagination of casual fans in the way that Beckham and Henry have, his signing would represent a coup for MLS.

He is a 31-year-old current captain of his country and a target for several European clubs. Garber says it would give MLS a "big boost of credibility," while it would also delight the large contingent of Mexican-American soccer fans.

As well as Beckham and Henry, current designated players include Colombian Juan Pablo Angel at New York, former Sweden international Freddie Ljungberg at Seattle Sounders, and U.S. international Landon Donovan at the Galaxy.

However, in all the incoming activity, the league may risk losing Donovan, its homegrown hero.

After a successful loan spell with English club Everton last season, Donovan says he is evaluating several transfer options and was also clear he would be happy to return to Goodison Park.

"I would love to go back to Everton -- I love the people there, I love the fans there," he told reporters after Wednesday's MLS All Star game against Manchester United, which ended in a 5-2 win for the English club.

(Editing by Stephen Wood)