The "Trump slump" that the travel industry warned about may be making an impact on America's tourism industry.

The number of international visitors arriving in the United States declined nearly 4 percent in the first six months of this year compared with the same period in 2016, according to data released Wednesday from the U.S. Department of Commerce National Travel and Tourism Office in Washington.

Many sectors of the travel industry have been warning that President Donald Trump's anti-foreigner rhetoric and immigration policies would lead to a drop in tourism here.

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Fewer visitors came from nearly every region of the world, with declines in arrivals from Western Europe, Eastern Europe, Asia, the Middle East, Africa, South America, Central America and the Caribbean.

The only region that sent more visitors in the first six months of 2017 compared with 2016 was Canada, up 5 percent.

The overall drop was even higher in June alone than for the six-month period, with a 6.7 percent decline in June 2017 compared with June 2016, the NTTO data showed.

All told, some 33.8 million non-resident international travelers entered the U.S. between January and June of this year, a 3.9 percent decline from the same period in 2016, the NTTO said.

A few numbers stood out. The decline from the Middle East was substantial at nearly 30 percent, January to June, year over year. Visitors from Mexico in June dropped 16 percent compared with the previous June, and there was a 9.4 percent decline in visitors from Mexico in the six-month period. Visitors from Western Europe were down just 1.8 percent for the six months.

"The latest government travel data is deeply concerning not just to our industry, but to anyone who cares about the economic well-being of the United States," Roger Dow, CEO of the U.S. Travel Association, a nonprofit representing the travel industry, said in a statement. "Travel is our country's No. 2 export and supports more than 15 million American jobs. These numbers are an undeniable wake-up call, and correcting this troubling trend needs to become a national priority."

NYC & Company, the tourism marketing agency for New York, also expressed dismay over the data. NYC & Company predicts that New York will lose up to 100,000 international visitors this year, its first drop in overseas arrivals since 2009. "The data released by the National Travel and Tourism Office underscores the concerns we have had this year about the international tourism landscape in the U.S.," said NYC & Company CEO Fred Dixon. The city has launched several promotions around the world to try to counter what Dixon described as the country's "vulnerability."

Other possible factors in the decline include the strength of the U.S. dollar against other currencies, which makes it expensive for travelers to vacation here, and headlines about gun violence, which may lead some travelers to choose other destinations out of safety concerns.

Travel experts like Arthur Frommer of the Frommer's guidebook company warned months ago that Trump's rhetoric and policies would lead to a "Trump slump" in travel, but earlier in the year, data was less definitive, possibly reflecting trips that had been planned by travelers before Trump took office.

The White House didn't immediately respond to a request for comment.