People hold a poster of Turkish President Recep Tayyip Erdoğan as they commemorate the first anniversary of the July 15, 2016 failed coup | Chris McGrath/Getty Images US lawmaker: Turkey’s purchase of Russian missile system may trigger sanctions Top US Senate Foreign Relations Democrat warns $2.5 billion Turkey-Russia deal might violate new sanctions law that Trump opposed.

Turkey’s recent purchase of an advanced Russian anti-air weapons system may have violated a U.S. law that would require an automatic imposition of sanctions on the NATO member, a top U.S. Democratic lawmaker said Thursday.

The letter, sent by Maryland Senator Ben Cardin to Trump administration officials, warns that Ankara’s purchase of Moscow’s S-400 air defense system, finalized Tuesday, violates congressional sanctions against Russia signed into law last month.

The legislation imposes sanctions “on any person that conducts a significant transaction with the Russian Federation’s defense or intelligence sectors,” wrote Cardin, the ranking Democrat on the Senate Foreign Relations Committee. The Trump White House resisted the sanctions as a congressional intrusion on presidential diplomacy.

“These are mandatory sanctions and constitute a commitment by the United States to deter Russia from attacking the United States and its allies in the future,” said Cardin’s letter to Secretary of State Rex Tillerson and Treasury Secretary Steve Mnuchin.

“As a U.S. ally, it is unfortunate that Turkey has appeared to align itself with Moscow during this critical time,” Cardin added.

The S-400 is Russia’s most advanced anti-air missile system and was originally designed to intercept U.S. strategic aircraft. It has a range of nearly 250 miles and can reportedly hit 80 targets at once.

Kremlin-funded media outlets like RT and Sputnik have trumpeted the deal as a diplomatic coup. In recent months, Moscow has worked to woo Turkey — a NATO member since 1952 — away from its Western military allies.

NATO officials have expressed unease about the $2.5 billion deal, both for its diplomatic implications and because of the introduction of Russian technology into the military hardware of a member state. No NATO country currently operates the system. An alliance spokesperson said it had not been informed about the details of the purchase but emphasized “It is up to allies to decide what military equipment they buy.”

In Ankara on Wednesday, Turkish President Recep Tayyip Erdoğan said NATO had only itself to blame because it has been slow to provide his country with requisite weapons systems.

NATO “went crazy just because we made the S-400 deal,” Erdoğan said, according to Turkish media. “What were we supposed to do? Wait for you? We are taking care of ourselves.” The Turkish leader acknowledged a deposit had been paid for the system, whose full price tag is $2.5 billion.

The State Department said the purchase would not meet NATO standards of having interoperable equipment among allies but stopped short of discussing potential repercussions.

On Tuesday, State Department spokeswoman Heather Nauert called the purchase “inconsistent” with a 2016 agreement to phase out Soviet-era military equipment among NATO allies.

The Pentagon also expressed concern over the purchase.

"We have relayed our concerns to Turkish officials regarding the potential purchase of the S-400," Pentagon spokesman Johnny Michael said in a statement. "A NATO interoperable missile defense system remains the best option to defend Turkey from the full range of threats in the region."

Cardin asked the administration to assess how the purchase might affect Turkey’s NATO membership as well as U.S. security assistance to Ankara, which includes arms sales. A freeze on U.S. weapons sale to Turkey was a topic of discussion at a Senate Foreign Relations Committee hearing last week.