WASHINGTON — From combat aircraft to ships, Middle Eastern countries are the biggest buyers of U.S. military equipment.

Between 2013 and 2017, the Middle East accounted for 49 percent of U.S. arms exports, according to a report by the Stockholm International Peace Research Institute. Saudi Arabia is America's No. 1 overall weapons buyer. In the last five years, Riyadh accounted for 18 percent of total U.S. arms sales, or about $9 billion.

Read more: Saudi Arabia is the top US weapons buyer – but it doesn't spend as much as Trump boasts

Saudi Arabia's oil-rich monarchy is one of America's most crucial strategic partners and a significant patron of U.S. defense companies. The Saudi defense deals, which have been brokered over multiple U.S. administrations, have recently come under scrutiny due to Riyadh's role in the Yemen war and the killing of journalist Jamal Khashoggi.

Saudi Crown Prince Mohammed bin Salman has denied knowledge of the attack on Khashoggi, although the CIA reportedly concluded that he ordered the writer's death. President Donald Trump, meanwhile, has cited the importance of defense deals in defending his decision to stick with the kingdom in the aftermath of the slaying.

The Saudis have agreed to purchase Lockheed Martin's Littoral Combat Ships for $6.5 billion and Raytheon's Patriot missile defense system for $1.6 billion.

In November, CNBC learned that Saudi Arabia signed a letter of offer and acceptance with the United States for Lockheed's THAAD missile system, a significant step forward in the $15 billion deal.

What's more, the Saudis are the top buyers in the British, Canadian, and Swiss defense markets, and spend heavily on Spanish, Swedish, Turkish and Finnish arms.

After Saudi Arabia, the United Arab Emirates are the next largest buyer of U.S. arms in the Middle East. The UAE is responsible for 7.4 percent, or about $4 billion, of sales.

According to the State Department, the Emirates' $1.9 billion for Boeing AH-64 Apache helicopters, Kuwait's $5.1 billion for Boeing's F/A-18 fighter jets, and Bahrain's $2.1 billion for Lockheed Martin's F-16 fighter make up some of the top sales to the Middle East.

All told, the U.S. State Department announced that the U.S. sold more than $55 billion in military equipment to foreign governments this fiscal year, which is a 33 percent increase from 2017.