According to an official statement presented by Saudi Arabia, the country will start the Ramadan fast on Thursday, May 17, as the crescent moon was not observable on Tuesday.
"On behalf of our family, Sophie and I wish all those observing this holy month a blessed and peaceful Ramadan".
The moon-sighting committee met at Abu Dhabi Judicial Department after Maghrib prayers on Wednesday to look for the new crescent Moon and determine when the holy month would begin.
"If, however, the crescent is not sighted that day, then, Friday, 18th May, 2018 automatically becomes the first of Ramadan, 1439 AH".
There are over 1,5 billion Muslims worldwide.
"We pray for peace, security, stability, and serenity around the world", Allam said in a video message.
Ramadan is the ninth month of the Islamic calendar and considered as the holiest month of the year by Muslims.
To mark the start of the Ramadan, UAE President Sheikh Khalifa sent cables to leaders of Arab and Muslim countries, reported state news agency Wam.
During the holy month of Ramadan, Muslims observe fast, perform acts of charity, recite prayers and read the Quran. After sunset the fast is broken with an evening meal called 'Iftar', often starting with few sips of water and handful of candies or dates.
This year, Ramadan falls on long summer days for Muslims in the Northern Hemisphere.