The 54-year-old won his first major in 1979 before he and countryman Jimmy Connors combined for nine Slams in the eighties, with Brian Teach and Michael Chang chipping in with one each.

Pete Sampras, Andre Agassi and Jim Courier meanwhile led the US to a decade of dominance in the 1990s with a combined 19 Slams between them, but the retirement last year of 2003 US Open champion Andy Roddick has left a vacuum.

"I think hopefully it's cyclical. We've had a pretty dry spell in the men. In the women we've had the Williams sisters and Sloane Stephens... she'll be in the top ten for sure. I think she's pretty close already," said McEnroe.

Stephens, currently ranked 17th, rose to prominence after beating her idol Serena Williams in the quarter-finals of the Australian Open.

She is among a raft of youngsters including fellow American Madison Keys who have been tipped as future stars.

Serena Williams meanwhile last month became the oldest woman at 31 to be ranked number one. But the top-ranked American man, 27-year-old John Isner, is currently well behind the leaders at number 15.

McEnroe said tennis would have to evolve into a more accessible sport and shed its image of an elite pastime to widen the net for future champions.

"Everyone in America and in other countries are looking for that next great player. The more that the game becomes accessible to youngsters and hopefully sexy in a way for kids to want to play in America -- I can't speak for every country. It's not that affordable.

"We had a great run for many years. You look at Australian tennis for example, they have an incredible history and they've been wondering.

"But they're a lot smaller country so there seems to be no reason why we couldn't find some players. We gotta find athletes and people who have the opportunity. You have to give more people the opportunity, it's really as simple as that."

Asked why American women had succeeded where the men had failed, McEnroe pointed to the economic opportunities tennis offers over other women's sports.

"For ladies one of the great things about tennis is the opportunity is there for them, more than virtually any other sport they play. They're given equal opportunity in terms of prize money, much closer to a fair shake growing up.

"And that's good and that's why you see a lot more girls in America turning to tennis than say American football, basketball, baseball, the other sports."

The seven-time Grand Slam champion was speaking at a press conference for the BNP Paribas Showdown in Hong Kong, where he got one-up on his former rival Ivan Lendl by winning 8-5 in a 'pro-set' organised for World Tennis Day.

In a closely fought encounter punctuated by periods of superb play mixed with basic errors, McEnroe showed slightly better fitness to edge his 52-year-old Czech-American rival, now Andy Murray's coach.

Though Lendl demonstrated greater power to hit several aces and counter-attacking baseline winners, McEnroe was able to break serve at 6-4 and held on to his advantage.

McEnroe closed out victory with a trademark serve-volley combo. Asked how the match compared to his playing career, he joked: "I think this is the biggest one of all. It's the match I will always remember."