The United Arab Emirates president, Sheikh Khalifa bin Zayed Al Nahyan has died at the age of 73.

Sheikh Khalifa has been battled with stroke since 2014. He’s rarely been seen in public and had longed ceased having involvment in day-to-day affairs.

His brother, Abu Dhabi’s Crown Prince Mohammed bin Zayed (known as MBZ) is seen as the de facto ruler and the decision-maker of major foreign policy decisions, such as joining a Saudi-led war in Yemen and spearheading an embargo on neighbouring Qatar in recent years.

The Ministry of Presidential Affairs announced that there will be 40 days of official mourning with flags at half mast and three days closure of ministries and official entities at the federal and local levels and the private sector,” the agency wrote on Twitter on Friday.

UAE has lost its righteous son and leader of the ’empowerment phase’ and guardian of its blessed journey,” MBZ said on Twitter, praising Khalifa’s wisdom and generosity.

Under the constitution, Vice President and Prime Minister Sheikh Mohammed bin Rashid Al Maktoum, the ruler of Dubai, would act as president until the federal council which groups the rulers of the seven emirates meets within 30 days to elect a new president.

Condolences started pouring in from Arab leaders, including Bahrain’s king, Egypt’s president and Iraq’s prime minister.

US Secretary of State Antony Blinken conveyed his condolences on the death of Sheikh Khalifa, whom he described as “a true friend of the United States”.

“We deeply valued his support in building the extraordinary partnership our countries enjoy today.

We mourn his passing, honour his legacy, and remain committed to our steadfast friendship and cooperation with the United Arab Emirates,” he said.

Sheikh Khalifa came to power in 2004 in the richest emirate Abu Dhabi and became the head of state.

He is expected to be succeeded as ruler of Abu Dhabi by Crown Prince Sheikh Mohammed.

Abu Dhabi, which holds most of the Gulf state’s oil wealth, has held the presidency since the founding of the UAE federation by Sheikh Khalifa’s father, the late Sheikh Zayed bin Sultan Al Nahyan, in 1971.

Sheikh Khalifa’s ruleSheikh Khalifa was born in 1948 in the inland oasis of al-Ain, near the border with the Sultanate of Oman, and named after his great grandfather, Sheikh Khalifa bin Shakhbout.

In 1969, while the area was still a British protectorate, Khalifa was named Abu Dhabi’s prime minister and chairman of the emirate’s Department of Defence, which later became the core of the UAE’s armed forces.

After independence in 1971, he became defence minister along with other roles and became president in 2004.

Although the UAE’s ruling sheikhs hold near-absolute power, Sheikh Khalifa began an experiment with elections by allowing limited voting – by a hand-picked electorate – for half the members of a 40-seat federal advisory body in 2006.

Subsequent rounds of elections in 2011 and 2015 failed to attract even two out of five of those given a chance to vote.

The UAE saw none of the Arab Spring street protests that shook other parts of the region, though, in the wake of that unrest, Khalifa oversaw tightening crackdowns on opposition activists, drawing criticism from international rights groups.

The UAE also supported efforts in the region to quash the Muslim Brotherhood, including in Egypt.

Sheikh Khalifa increasingly used Abu Dhabi’s oil wealth to attract cultural and academic centres, such as branches of the Louvre Museum and satellite campuses of New York University and the Sorbonne.

He also presided over efforts to move the OPEC country beyond its reliance on petrodollars with investments in renewable energy research, including plans for a futuristic low-carbon desert city known as Masdar.

seas during Sheikh Khalifa’s rule also helped push the emirate, which controls the bulk of the UAE’s oil reserves, out from the shadow of Dubai, the Middle Eastern commercial hub.

As Dubai’s fortunes began to falter along with the global economy in 2009, Sheikh Khalifa led efforts to protect the federation by pumping billions of dollars in emergency bailout funds into Dubai.

The two emirates do not always see eye-to-eye on foreign policy decisions and compete commercially with one another. In 2003, he called for the creation of a new airline, Etihad Airways, which competes with Dubai’s successful and much larger carrier Emirates Air.

Sheikh Khalifa also helped boost the UAE’s regional profile with relief missions to Pakistan after devastating floods and by sending warplanes to the NATO-led mission against Muammar Gaddafi’s rule in Libya in 2011.

Questions were raised during Sheikh Khalifa’s rule about the UAE’s use of foreign military contractors, including one linked to the founder of the former Blackwater security firm, Erik Prince, who moved to Abu Dhabi in 2009.

Prince was involved in a multimillion-dollar programme to train troops to fight pirates in Somalia, according to an official who spoke to The Associated Press news agency in early 2009.

Sheikh Khalifa’s name is perhaps most familiar around the world for its connection to the world’s tallest building, a nearly 828-metre (half-a-mile) glass-and-steel spire in Dubai.

The name of the tower was unexpectedly switched from the Burj Dubai to the Burj Khalifa at its official opening in January 2010 following his decision to funnel billions of dollars to Dubai to save it from a full-scale financial meltdown.

He was believed to be among the world’s richest rulers with a personal fortune estimated by Forbes magazine in 2008 at $19bn.

He is known to have had eight children – two sons and six daughters – with his first wife, Sheikha Shamsa bint Suhail Al Mazrouei.

He is also survived by several grandchildren.