The US Travel Association says the Trump administration’s immigration policies are hurting tourism.

The non-profit industry organisation said in a statement that there were mounting signs of “a broad chilling effect on demand for international travel to the United States”.

White House spokeswoman Lindsay Walters disputed the contention.

“It takes several months for each month’s international arrival statistics to be processed and released to the public,” Ms Walters said.

“To claim the executive order has had an impact on travel would be premature.”

But the US Travel Association’s statement has added to a growing chorus of concern from the travel industry over the impact of Trump administration policies on tourism.

Earlier this week, the tourism agency NYC & Company revised its 2017 forecast to predict a drop in inbound international travel to New York City, with 300,000 fewer visitors compared to 2016.

It would be the first drop in visitation to New York since the start of the recession in 2008.

The Philadelphia Convention and Visitors Bureau told the Philadelphia Inquirer this week that it had missed out on an international meeting with 3000 attendees that decided to go to Canada or Mexico instead.

And ForwardKeys, which tracks travel bookings, reported in February that international trends in bookings to the US were down 6.5 per cent compared with the equivalent period the year before.

“It’s known as the Trump Slump,” travel guru Arthur Frommer wrote last month on Frommers.com.

He called it “an unintended consequence of the Trump-led efforts to stop many Muslims from coming to the US”, resulting in “a sharp drop in foreign tourism to our nation that imperils jobs and touristic income”.

US Travel Association president Roger Dow said there was concern that many international travellers had interpreted President Donald Trump’s policies as “wanting to discourage international visitors generally, not just those who pose a security risk”.

Mr Trump’s initial ban on travellers from Iran, Iraq, Libya, Somalia, Sudan, Syria and Yemen was suspended after a court order, but a revised executive order on visas and immigration is expected soon.

The US Travel Association urged the administration to make clear in any revised order “that the US welcomes and values legitimate international business and leisure travellers”.

Tourism is an enormous sector of the US economy, generating $US2.1 trillion ($2.8 trillion) in economic output and supporting 15.1 million jobs, with international visitors a key component, according to data from the US Travel Association.

“Security is a top priority for the US travel community, but it’s critical to balance both sides of the ledger: make clear who is not welcome, but also who remains welcome,” Mr Dow said.

A January 30 opinion piece in the Toronto Star newspaper encouraged Canadians to “boycott vacations to the US” until Mr Trump is no longer president.

NYC & Company is launching a new campaign called “New York City — Welcoming the World” to try to counteract the expected downturn.

The agency said in a press release that the campaign was intended to reassure international travellers who might feel deterred about travelling to the US that they were welcome in New York.

But Alexandre de Juniac, head of the International Air Transport Association, said on Thursday that industry leaders were not worried about a downturn, and that air travel to the US “still looks positive in 2017”.

George Aguel, president of Visit Orlando on Disney’s Florida turf, said “it would be premature to determine if there is a potential decline in overall international visitation to our region, and if any such decline can specifically be attributed to the administration’s executive orders”.

Another factor in a potential downturn could be the strong US dollar, which has made it more expensive for international visitors to holiday there.

Last year, the US Commerce Department predicted a record 78.6 million international visitors would go to the US in 2017.

That forecast is usually updated in May.