The number of overseas visitors to the US is falling, with a 5.4 per cent drop in March compared to the same time last year.

It represents the worst showing since 2015, prompting fears among the country's tourism chiefs that the US will lose out to rival destinations this year.

Tourism also fell in February, albeit by a more modest 0.2 per cent, figures released by the US Travel Association revealed.

These figures have fuelled concern in an industry which has also been beset by labour shortages because of difficulties bringing in seasonal workers from overseas as a result of the Trump administration's tougher line on visas.

"The outlook for international inbound travel remains lacklustre, suggesting that a further loss of global market share is in the cards for the US in 2019," said David Huether, Senior Vice President for Research at US Travel, the industry trade association.

Tourism is vital to the US economy, representing 11 per cent of the country's total trade surplus of $77.4 billion.

Last year, international tourism generated $197 billion for the US economy.

The economic importance of tourism was recognised by the Obama administration, which passed the Travel Promotion Act to boost the industry.

It saw heavy investment in technology to cut airport immigration delays and established Brand USA to spearhead a global tourism campaign.

Tourism slumped in the aftermath of Donald Trump's election, with visitors being put off by the rhetoric coming from the White House and the furore surrounding the attempt to ban people from several Muslim majority countries.

Although the controversy has abated, official figures suggest that US immigration officials are continuing to take a tougher line than before.

According to statistics produced by Customs and Border Protection, just over 279,036 people were denied entry into the US at ports of entry in 2018 compared with 216,370 in 2017. So far this year 163,377 have been turned away.

But other factors appear to be underpinning the disappointing numbers, including the strength of the dollar which has made US holidays more expensive.

Oxford Economics, in a report commissioned by the industry, warned that this represents "a headwind for international inbound travel."

"Soft global economic activity, persistent trade tensions and uncertainty surrounding the Trump administration remain major risks to international traveller sentiment," it added.

The US share of the international long-haul market has been falling from a peak of 19.2 per cent in 2015 to 16.8 per cent last year.

Concern in Europe over the Brexit negotiations and the trade war between Beijing and Washington – which saw a double-digit slump in Chinese tourism to the US - are also seen as factors driving tourism down.

The industry's difficulties have been exacerbated by problems finding staff to work in hotels and restaurants.

With the economy booming, there are not enough Americans available to fill the vacancies, leaving the tourism industry to rely on seasonal workers who are allowed into the country on the H-2B visa programme.

Have you avoided visiting the US in the last few years? If so, why? If not, what has made you want to visit? Tell us in the comments section below.