Kuwait on Wednesday swore in its new emir Sheikh Nawaf al-Ahmad al-Sabah, who pledged to preserve the country's unity and stability.
The 83-year-old Sheikh Nawaf, the former crown prince of Kuwait, succeeds his half-brother, Sheikh Sabah al-Ahmad al-Sabah, who died Tuesday at the age of 91.
The late ruler's body is due to arrive back in Kuwait on Wednesday.
"With great sadness and sorrow, we mourn to the Kuwaiti people, the Arab and Islamic nations, and the friendly peoples of the world, the death of the late His Highness Sheikh Sabah al-Ahmad al-Jaber al-Sabah, Emir of the State of Kuwait who moved next to his Lord," the royal palace said in a Tuesday statement, according to Kuwaiti state television.
Two months ago, Sheikh Sabah was flown to the U.S. aboard a U.S. Air Force C-17 flying hospital after undergoing surgery, according to NBC News.
Before assuming power in 2006, he was Kuwait's top diplomat, and during that time, he worked to mend fences with Iraq, fractured since the 1990 Gulf War, which saw a coalition of forces, led by the U.S., liberate Kuwait after Iraq invaded.
Sheikh Sabah hosted donor conferences to raise money for Iraq, Syria and other war-torn countries. He also worked to ease continuing tensions between Qatar and other Arab states.
A spokesman for U.N. Secretary-General Antonio Guterres called Sheikh Sabah a "close friend of the United Nations" who "always sought to strengthen relations for the shared goal of sustaining peace and stability in the region and around the world."
"His Highness was a distinguished statesman and an outstanding humanitarian who contributed to building bridges of understanding in the Gulf region and beyond," the spokesman added.
Internally, Sheikh Sabah's tenure was marked by strong political rivalries, the 2011 Arab Spring and unstable oil prices, AP reported.
"He represents the older generation of Gulf leaders who valued discretion and moderation and the importance of personal ties amongst fellow monarchs," said Kristin Diwan, a senior resident scholar at the Arab Gulf States Institute in Washington, speaking with AP. "No question he has suffered from the lack of deference and respect shown by the younger and more brash young princes holding power today."
Sheikh Nawaf is the 16th ruler in Kuwait's al-Sabah dynasty, which dates to 1752. He is the sixth emir since Kuwait gained independence from Britain in 1961.