The Covid-delayed Expo 2020 kicks off in Dubai on Thursday with an extravagant opening ceremony for what is expected to be the world's biggest event since the start of the pandemic.

Dubai's edition of the global fair, the first ever held in the Middle East, hopes for 25 million visitors over six months to its gleaming pavilions in the desert.

Dubai's ruler Sheikh Mohammed bin Rashid Al-Maktoum is at 1640 GMT to open the event grouping more than 190 countries which he has promised will be "the most exceptional Expo in the history of the event".

The Expo site in the dusty Dubai suburbs has remained strictly off-limits during its year-long postponement. 

Architectural marvels and a long list of technological innovations will feature among the exhibits, showcasing the ingenuity and technological innovations of the participating countries.

The first world fair was held in London in 1851, when it was housed in the purpose-built Crystal Palace, and the Paris edition of 1889 featured the Eiffel Tower, at first intended as a temporary attraction.

Expo 2020 will be indelibly tinged by the pandemic, with masks and social distancing mandatory on site. Visitors will need to be vaccinated or have a negative PCR test to enter.

The United Arab Emirates, population 10 million, has reported rapidly dwindling coronavirus cases in recent weeks, dropping below 300 on Sunday -- less than half the figure a fortnight earlier.

Robot panda, ancient coffin 

The fair is another feather in the cap for Dubai, which has long strived for recognition with achievements such as the Burj Khalifa, the world's tallest building at 828 metres (2,717 feet).

The postponement has worked out well in one respect for the UAE, as it celebrates the 50th anniversary of its founding on December 2. 

Workers have been putting the final touches on infrastructure and facilities at the site this week as the clock ticked down to the delayed launch.

A succession of politicians, business leaders, celebrities and sports people are expected at the Expo, whose diverse attractions include the Harlem Globetrotters and a Chinese robot panda.

A full-scale hyperloop cabin, touted as the future of long-distance travel and transport, is among the exhibits, while Egypt has imported an ancient coffin from pharaonic days.

China has one of the largest pavilions -- a LED-lit, lamp-shaped creation -- while Morocco's is made with traditional mud-building methods.

Israel is also gearing up to take part, a year after the UAE and the Jewish state normalised ties.