President Trump’s plans to restrict immigration into the United States risk jeopardizing Silicon Valley’s success, Irish billionaire John Collison has said.

The 27-year-old Limerick man and Bay Area resident told the New York Times that he thinks the US tech industry’s future is “fragile” and would risk ruin without immigrant labor.

“The U.S. is sucking up all the talent from all across the world,” Collison insisted. “Look at all the leading technology companies globally, and look at how overrepresented the United States is. That’s not a normal state of affairs. That’s because we have managed to create this engine where the best and the brightest from around the world are coming to Silicon Valley.”

Collinson founded his company, Stripe, six years ago in San Francisco alongside his older brother Patrick. The company allows business and individuals to make financial payments over the internet and has in just a few short years has earned the pair in excess of $1 billion each. In November 2016 the two were proclaimed the world’s youngest ever self-made billionaires.

However Collinson doesn’t believe Stripe’s success happened just by chance; far from it, it was the unique melting pot of Silicon Valley that facilitated the company’s growth and made it the global brand it is today.

“Silicon Valley is unlikely, as a phenomenon — it is not the default state of the world,” he told the NY Times. “I go all across the world, and every other place is asking, ‘How do we replicate Silicon Valley where we are — in London, in Paris, in Singapore, in Australia?’”

For him the answer is simple: the world’s best and brightest tech graduate flock to California. Were it not for immigrants, like him and his brother, Collinson believes the project might never have gotten started. “In the early stages of a start-up you usually have a very specific set of things you need to do, and there’s a very short list of people who are able to do them… the talent is here or that we can bring the talent here, that’s what makes the whole thing work,” he said.

This openness to, even celebration of immigration, sits uneasily with Donald Trump’s vision of America. Most tech workers are hired on H1-B visas which the new Administration has promised to clamp down on.

Despite previously having used the H1-B visa himself to bring models into the country, President Trump pledged to curtail the visa on the campaign trail last year.

“I will end forever the use of the H-1B as a cheap labor program, and institute an absolute requirement to hire American workers first for every visa and immigration program. No exceptions,” he said whilst still a candidate for the GOP nomination.

And he’s likely to find support from Congress on this issue. His former rival for the Republican party nomination, Ted Cruz, introduced legislation in the Senate to restrict access to the visa and California Congresswoman Zoe Lofgren has proposed H-1Bs be issued only to people with salaries in excess of $130,000.

600 Irish citizens obtained H1-B visas in 2015 - many of whom go to be issued with green cards. However, critics of the program maintain it is simply a way for employers to import cheap, foreign labor into the US and research suggests that there are currently a sufficient number of American college graduate to fill vacancies in the industry.

Other research suggests that immigrants to the US are disproportionately represented among the founders of America’s most successful start ups. The independent think tank the National Foundation for American Policy found that of the 87 US startups worth more than $1 billion more than half were founded by those born overseas and a further 71% of those same startups employed immigrants in top management positions.

Other programs used to temporarily bring foreign workers into the US also look likely to be cut back. The J-1 visa used by thousands of Irish college graduates to come and work in America after their graduation for a further three years last December but on the campaign trail then candidate Trump pledged to abolish it. On his website he declared the J-1 would be, “terminated and replaced with a resume bank for inner city youth provided to all corporate subscribers."

So apparently Donald Trump wants to get rid of au pairs since we are all here with a J-1 Visa ?✌?️ pic.twitter.com/OLaJP8Nokx

— Annie. (@CallMeAnnie) May 7, 2016

Exciting day for #USIreland relationship; we've extended our Memorandum of Understanding for the Ireland Work & Travel #J1Visa Program. pic.twitter.com/hpStina5PB

— Mark Taplin (@ECA_AS) December 6, 2016

The promise has since disappeared from his website but as the White House seeks to reduce “immigration levels, measured by population share, [to] within historical norms,” it looks like it won’t just be Silicon Valley that will find it harder and harder to bring new talent into America.

Update regarding J1 Visa... The proposal regarding the J-1 program is no longer mentioned on the Trump campaign website. @AmeriCamp #J1Visa pic.twitter.com/7fNovXIRYp

— Lee McAteer (@MrLeeMcAteer) November 10, 2016