Tourism in Northern Ireland is more vulnerable to Brexit than any other region because it relies on the British market for the majority of its income from the sector, it has been claimed.
Tourism Ireland chief executive Niall Gibbons said the withdrawal of the UK from the EU was the single "biggest risk factor" for the tourism sector.
Visitors numbers to Northern Ireland are expected to reach more than 2.2 million by the end of 2018.
British visitors are expected to account for more than 60% of that figure.
"It's an extremely important industry," he said.
"Northern Ireland is more vulnerable than other areas because of its high dependency on the number of British tourists.
"We know from our research that if more people in Britain decide to stay at home it's more likely that Devon and Cornwall, the Lake District and Scotland would be the winners than Northern Ireland, the Isle of Man and Channel Islands because it involves getting a plane or a boat."
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Mr Gibbons added: "It is more vulnerable because it does rely on the GB market for about nearly 70% of all its business."
He said a deal needed to be reached to ensure economic certainty and stability within the industry.
He added: "When people are feeling uncertain, and if their pocket is going to get hit, the first thing that gets hit is discretionary spending which often is tourism.
"It's important that a deal gets done... because ultimately consumers require certainty in their lives, that's what keeps them travelling."
Mr Gibbons said contingency planning was already well under way in the cross-border organisation, which promotes the island of Ireland overseas as a holiday destination.
Tourism Ireland received an additional €10 million (£8.9 million) from the Dublin government to bolster marketing efforts abroad and counter Brexit uncertainty.
Mr Gibbons said Tourism Ireland will be launching a worldwide marketing campaign for 2019 that will be rolled across mainstream TV in the UK.
"The ad campaign will reach 40% of all GB adults in our target market," Mr Gibbons said.
He added: "We're still looking to grow visitor spend from Britain next year, but that could have to change if things change in the next weeks and months.
He said the bottom line was that global travel would continue next year.
"The British market is important, that's 70 million people, but there will be 1.3 billion people around the globe taking holidays next year and we've to make sure we're positioned for that too," Mr Gibbons said.
