(Bloomberg) -- Turkey has taken its case for buying a Russian air-defense system directly to President Donald Trump, in a last-ditch effort to defuse tensions between the two NATO allies.

“We delivered our message and received quite positive feedback,” Treasury and Finance Minister Berat Albayrak told reporters on Monday, after he presented the U.S. president with an explanation for why Turkey needs the missiles that have raised questions about the nation’s alliance with the West. It’s likely to use the advanced system to defend Istanbul, the country’s commercial center, and its capital Ankara, according to Defense Minister Hulusi Akar.

Turkey has stood by the agreement with Russia and described it as a “done deal” despite serious U.S. objections. The Trump administration has threatened sanctions if the country goes ahead with the purchase. The warning risked intensifying market turmoil, echoing the reaction to a diplomatic standoff last year.

The first batch of S-400 missiles may be delivered as early as June. Future deliveries might involve technology transfer to Turkey, Akar told reporters who traveled to Washington, where the defense chief was meeting with American officials. Albayrak, the Turkish president’s son-in-law, said he also met Trump’s son-in-law, Jared Kushner.

President Recep Tayyip Erdogan’s decision to purchase the Russian military equipment has damaged relations between Washington and Ankara. The U.S. says the S-400 system was designed to shoot down American and allied aircraft, including Lockheed Martin Corp.’s F-35 Joint Strike Fighter, which Turkish manufacturers help build. American officials have threatened to expel Turkey from the F-35 program.

Turkey says it needs the Russian system because it currently lacks the capability to defend itself from aerial attacks. Ankara is proceeding on the assumption that it will receive F-35s and will use them alongside the S-400, Akar said.

Patrick Shanahan, the acting U.S. defense secretary, has called Turkey’s planned purchase of the S-400 “incompatible” with the sale of F-35s. U.S. officials have said they’re concerned that sensitive F-35 technology designed to evade such a system could be compromised and used to improve Russian air-defense technology.

The Turkish defense chief tried to play down that threat, saying the S-400 would operate independently from systems used by the North Atlantic Treaty Organization. Turkey is a member of the NATO alliance.

“Turkish-American ties can’t be disregarded,” Akar said a day before his planned meeting with Shanahan. "Our hope and wish is that these meetings will make it possible to find a solution to the problems."

The U.S. offered Ankara its Patriot missiles on a faster delivery schedule. But that attempt went nowhere. There’s another standing offer by the U.S. to sell Turkey the Patriot system and there’s no deadline on it, Akar said, without elaborating.

When asked about the possibility of receiving the S-400 system, but not deploying it to avert further American pressure, Akar said: “These are all options. Let’s see what the process ahead will bring.”

To contact the reporter on this story: Firat Kozok in Washington at fkozok@bloomberg.net

To contact the editors responsible for this story: Onur Ant at oant@bloomberg.net, ;Alaa Shahine at asalha@bloomberg.net, Paul Abelsky, Riad Hamade

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