MOSCOW – Russia will deliver its S-400 air-defense missile system to NATO-member Turkey in the coming days, a Kremlin spokesman said Friday, in a deal likely to trigger U.S. sanctions and test the bonds of the Western military alliance. But the scope of the possible response from Washington remains clouded by apparent conflicting messages. President Donald Trump has publicly shown sympathy for Turkish President Recep Tayyip Erdogan’s position on the Russian missile purchase. Secretary of State Mike Pompeo, however, has warned of tough measures that could include canceling the sales of F-35 fighter jets to Turkey. For the wider NATO alliance, the Turkish deal strikes at the heart of military coordination. NATO has expressed worry that the S-400 is incompatible with its possession of the U.S.-made F-35s, and would give Russia access to secrets of its stealth technology. For more than a year, the United States has urged Erdogan not to procure the sophisticated Russian air-defense system – a move that would bring mandatory U.S. sanctions against Turkey under a 2017 law on cooperation with “adversaries.” The U.S. measures, if carried out, would cause an extraordinary breach in U.S.-Turkey relations and almost certainly complicate ongoing negotiations between the two countries over other issues, including military strategy in Syria. But while U.S. officials have portrayed the sanctions against Turkey as a matter of certainty, Trump refrained from taking a hard line with Erdogan over the S-400s during talks last month at the Group of 20 summit in Japan. Trump noted that Turkey help bring U.S. jobs by paying a “tremendous amount of money” on the F-35 fighters. Trump, speaking to reporters at the summit, said Erdogan had first sought to buy Patriot missiles but had been “treated very unfairly” by the Obama administration, without giving specifics. But the United States had attempted to strike a deal with Ankara over the Patriot systems. Erdogan insisted that any deal include sharing technology so that Turkey can develop and build its own missiles. The Obama administration declined the offer. At the G-20 summit, Trump did not directly answer questions about whether the United States would impose sanctions on Turkey. Erdogan, however, said after his talks with Trump that Turkey would be spared the U.S. sanctions. Erdogan has portrayed the purchase as Turkey’s sovereign right and said that the United States failed to offer a comparable deal for the Patriot missile system. Asked by a reporter during a telephone briefing if Russia would deliver the system on Sunday, Kremlin spokesman Dmitry Peskov said, “I can confirm on behalf of the Kremlin that the S-400 deal is going according to plan.” Turkey’s private broadcaster Haberturk said the first shipment of the S-400s would be loaded onto cargo planes on Sunday and arrive in Turkey sometime next week.Washington has threatened to impose sanctions in response to the purchase of the Russian system, under the Countering America’s Adversaries Through Sanctions Act, which mandates U.S. sanctions against anyone making a “significant” deal with the Russian defense industry. U.S. officials have vigorously insisted over the last year that the only way for Turkey to avoid such sanctions was to abandon its purchase of the S-400’s. The State Department Friday repeated its previous warnings that Turkey is exposing itself to sanctions. “The United States has consistently and clearly stated that Turkey will face very real and negative consequences if it proceeds with its S-400 acquisition, including suspension of procurement and industrial participation in the F-35 program and exposure to sanctions,” said a State Department spokesman. Last month, the Pentagon, in a show of determination, said it would halt the training of Turkish pilots to fly the U.S.-made F-35 warplane. India also wants to buy S-400s from Russia, and it has defied the threat of U.S. sanctions by finalizing a deal to buy five S-400 batteries for $5.4 billion. Russia supplies many weapons systems to India. India has asked for waivers from U.S. sanctions, and the deal complicates the administration’s desire to expand trade and diplomatic relations with New Delhi. U.S. officials have said they are “urging” India not to buy the Russian missile system and “encouraging” it to find alternatives so as not to trigger sanctions. But during Pompeo’s visit to New Delhi last month, India showed little sign of backing down. Asked about the S-400 purchase in a press conference with Pompeo, Foreign Minister Subrahmanyam Jaishankar replied that India will act in its national interest, and noted that its relationships with other countries “have history.” Pompeo said the two countries are friends and partners, and vowed to “find a way to work through” the differences.