King Abdullah of Saudi Arabia died on early on Friday at the age of 90, according to a statement released by the Royal Court. King Abdullah took the throne at a later age and was known as a "cautious reformer," even in the face of threats by Islamic State, according to The New York Times.

The New York Times reports that the Royal Court did not disclose the cause of the King's death, but a translation of the announcement suggests, "the presence of pneumonia," and the need for a breathing tube. U.K.'s The Telegraph also reports the king's death as a result of pneumonia. King Abdullah was admitted to a Riyadh hospital on Dec. 31 with a lung infection.

Saudi Arabia is a close ally of the United States and the world's largest exporter of oil. Abdullah's half-brother, Deputy Prime Minister Salman bin Abdul Aziz, announced his brother's death on television and revealed that he (Salman) had assumed the throne, according to NBC News. King Salman is 80-years-old.

The funeral will be on Friday and mourning will continue for three days.

A full statement from President Barack Obama was released via The White House:

"It is with deep respect that I express my personal condolences and the sympathies of the American people to the family of King Abdullah bin Abdulaziz and to the people of Saudi Arabia.

"King Abdullah's life spanned from before the birth of modern Saudi Arabia through its emergence as a critical force within the global economy and a leader among Arab and Islamic nations. He took bold steps in advancing the Arab Peace Initiative, an endeavor that will outlive him as an enduring contribution to the search for peace in the region. At home, King Abdullah's vision was dedicated to the education of his people and to greater engagement with the world.

"As our countries worked together to confront many challenges, I always valued King Abdullah's perspective and appreciated our genuine and warm friendship. As a leader, he was always candid and had the courage of his convictions. One of those convictions was his steadfast and passionate belief in the importance of the U.S.-Saudi relationship as a force for stability and security in the Middle East and beyond. The closeness and strength of the partnership between our two countries is part of King Abdullah's legacy.

"May God grant him peace."

Vice President Joe Biden will travel to Saudi Arabia as he leads a presidential delegation representing the United States, according to NBC News. A statement from the office of the vice-president relayed the following message: "King Abdullah's death is a great loss for his country. It is hard to distinguish him from Saudi Arabia itself. Over many decades, he played an outsized role in building his country.

"I always appreciated [King Abdullah's] frankness, his sense of history, his pride in his efforts to move his country forward, and his steadfast belief in the U.S.-Saudi relationship."

Prince Charles will likely attend any funeral services for Abdullah as Queen Elizabeth's representative, as the Queen does not make long-distance travel anymore, according to The Telegraph.