The first world fair to be held in the Middle East, Expo 2020 Dubai, opens its doors to exhibitors from almost 200 countries on Oct 1 after being delayed for a year by the coronavirus pandemic.

Dubai officially expects 25 million visitors, more than twice the population of the United Arab Emirates. All those over 18 will have to be vaccinated against coronavirus or test negative to enter, according to a Reuters report.

But diplomats from five different countries said they had revised down their national pavilions' visitor targets. James Swanston, an economist at Capital Economics, said the continuing obstacles to foreign travel meant the economic boost was likely to fall short of projections.

Many events will be streamed live online.