U.S. Defense Secretary Mark Esper discussed "strategic cooperation" with Saudi King Salman Tuesday, days after Washington ordered thousands of soldiers to the kingdom as tensions fester with Iran.

The meeting in Riyadh, where Esper arrived late Monday after an unannounced visit to Afghanistan, also took in defense issues and the current situation in the region, the official SPA news agency said.

The report also said that Esper had met Crown Prince Mohammed bin Salman, who is also defense minister, and the two discussed "military and defense cooperation."

On October 11, the Pentagon said it was deploying new U.S. troops to Saudi Arabia after Riyadh asked for reinforcements following a mid-September drone and missile attack on Saudi oil plants, which Washington blames on Iran.

Esper has said that two fighter squadrons and additional missile defense batteries were being sent to Saudi Arabia, bringing to about 3,000 the total number of U.S. troops deployed to the kingdom since last month.

The September 14 attack knocked out two major facilities of state oil giant Aramco in Abqaiq and Khurais, roughly halving Saudi Arabia's oil production. Washington condemned the attacks as an "act of war," but neither Saudi Arabia nor the United States has overtly retaliated.

Tensions have soared in the Gulf in recent months with a series of attacks on oil infrastructure and tankers, raising fears of war. Iran has denied any involvement.

The U.S. has dispatched about 14,000 more U.S. troops into the region since May, beefing up efforts to defend the kingdom in the wake of suspected Iranian missile and drone attacks on oil facilities last month.

Despite the additional troops, President Donald Trump's sudden withdrawal of forces from northeastern Syria has raised questions about Washington's commitment to allies and opened the door for Russia to increase its regional influence.

The move was criticized as a betrayal of Kurdish allies who fought for years alongside U.S. troops against ISIL.

Esper said on Monday that at least some troops might stay to deny ISIL militants and others access to oil fields.

(Cover: U.S. Defense Secretary Mark Esper is welcomed by Saudi Arabia's Deputy Defense Minister Prince Khalid bin Salman, in Riyadh, Saudi Arabia, October 21, 2019. /Reuters Photo)

(With input from AFP and AP)