(Bloomberg) -- President Vladimir Putin said Russia is willing to help defend Saudi Arabia by selling it the advanced S-400 anti-aircraft system after major oil facilities in the kingdom came under attack at the weekend, halting half of its crude production.

“For self-defense, for the defense of one’s country, we are ready to provide help to Saudi Arabia, the political leadership of Saudi Arabia,” Putin told a joint press conference with the leaders of Iran and Turkey on Monday in Ankara.

“It is enough to take a wise government decision, as the leaders of Iran did before, buying the S-300, and as President Erdogan did, buying the latest air defense system, S-400 Triumph,” Putin said, referring to the Turkish president. “They will protect any infrastructure objects in Saudi Arabia effectively.”

Riyadh has been in talks with Russia on purchasing the S-400 but going through with the deal would risk U.S. sanctions. Russia’s success in persuading President Recep Tayyip Erdogan’s administration to buy the S-400 provoked a rift between Washington and Turkey, a NATO member and long-time U.S. ally. In response, the Trump administration suspended Turkey’s ability to build and buy the advanced F-35 warplane.

In the addition to the immediate loss of oil output, equivalent to 5% of world supply, the attack claimed by the Iranian-backed Houthi rebels in Yemen raised the specter of U.S. retaliation against Iran, which American officials have blamed for the operation.

Putin said Yemen’s conflict between the Houthis and the United Nations-recognized government backed by a Saudi-led coalition needs to be resolved, pointing to the existence of a “humanitarian catastrophe” in the Middle East country after more than four years of fighting.

To contact the reporter on this story: Henry Meyer in Moscow at hmeyer4@bloomberg.net

To contact the editors responsible for this story: Gregory L. White at gwhite64@bloomberg.net, Torrey Clark, Onur Ant

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