Negotiations to hold a major European conference at Belfast's Waterfront Hall were halted because of Brexit.
A European company pulled out of talks late last year for an event in 2020 which would have boosted the local economy.
Despite the setback, a spokesman said the venue had a "strong pipeline" of future events booked.
The Waterfront Hall has greatly expanded in recent years with the aim of attracting large conferences.
A spokesman for Belfast Waterfront said: "Subsequent to the decision of the UK to leave the European Union, one European-based organisation who we had been in preliminary negotiations with stated it could no longer consider Belfast for its conference in 2020.
"This was due to funding restrictions limiting the conference venue to EU member states.
"Belfast Waterfront has a strong pipeline of conferences and events booked for 2018, 2019 and beyond."
The identity of the company has not been disclosed for commercial reasons.
In 2016 the new extended Waterfront Hall opened at a cost of nearly £30 million.
It has held a series of major conferences focusing on sectors like technology and law.
The Waterfront's managing director Catherine Toolan outlined details in a recent meeting of an oversight committee at Belfast City Council.
A record said: "She explained that conferences were key to Belfast Waterfront and Ulster Hall Ltd and that the recent declaration by Lonely Planet that Belfast and the Causeway Coast was the best region to visit in 2018 was certainly beneficial and would hopefully put Belfast on the map.
"She outlined that transportation, particularly direct flights, was one of a number of key considerations for most conference organisers."
Belfast Waterfront doubled in size as part of its overhaul to create an international venue capable of attracting major conferences with a fully flexible and integrated space catering for up to 5,000 delegates a day.
At one stage it aimed to generate £100 million for Belfast and create 1,500 new jobs by attracting 50,000 conference delegate days each year by 2020.
A major programme of hotel building this year to cater for the influx of business and leisure travellers has helped reshape the city's skyline.