LONDON (Reuters) - Ask U.S. national rugby sevens head coach Mike Friday how he feels to be in charge of a nascent sporting superpower, and he winces.

While the United States is seen by some as the key to driving global growth in the Olympic sport, and ultimately unlocking the Chinese market, Friday has more immediate concerns.

“Currently our squad live on the poverty line,” the Briton, a former 15s player with Wasps and Harlequins, told Reuters ahead of the annual HSBC London Sevens event at Twickenham this weekend.

“You wouldn’t have thought an international rugby athlete should be living on the poverty line but that’s where we are at the moment.

“I’m not talking about earning what they earn in the NFL, I’m talking about being able to take your wife out for a meal or taking your kids for ice cream.”

Figures released by the HSBC World Rugby Sevens Series on Wednesday trumpeted strong growth on the back of the Rio de Janeiro Games, with projected total attendances up seven percent on last year.

They showed an estimated 18.6 million new rugby fans in six markets, with participation levels revealing an eight percent increase on 2015 levels. Sevens had a social media reach of 120 million.

Giles Morgan, global head of sponsorship and events at sponsor HSBC, said the sport was still just scratching the surface in terms of interest and attendance.

Success for the United States at the 2020 Tokyo Games could be transformational for a game that is growing fast in the Americas, he added.

“If a gold medal for the USA happens, I believe other countries in the far east such as China will really start to invest in sevens,” he told Reuters.

“And then you have genuinely the start of a global game...to get the seismic change and really dramatic shift in numbers, I think it starts with the USA and will end with China.”

The U.S. men have had some strong results in the sevens series, but Morgan estimated it would take 20 years for the new world order to emerge fully.

Friday, who said $3 million was needed as an annual budget and he had only half of that, agreed the potential was there and hosting the 2018 World Cup Sevens in San Francisco would be important for momentum.

But operating on a shoestring in the home of the NFL, basketball and other “super sports” was tough.

Friday said rugby needed to be positioned in high schools and colleges as a complement to other sports, rather than as a competitor. For those that didn’t make it in the NFL, rugby offered an Olympic goal.

“Retention and losing athletic ability to ‘Civvy Street’ too early is a huge issue for us...but if we can retain this group and continue to move forward, could we be (Olympic) medal contenders (in 2020)? Absolutely,” he said

“I keep telling our squad ‘you’re pioneers’. You’ve got to deliver on the pitch to make this an aspirational game. Americans love success.”