The United States moved closer to a full-blown crisis with fellow NATO member Turkey after Ankara said the first parts of the S-400 Russian missile defense systems had been delivered on July 12 and that more deliveries will follow.
However, the U.S. administration remained silent on how it would respond, and a news conference scheduled for later in the day to explain its potential action was postponed "indefinitely."
The U.S. acting defense secretary, Mark Esper, spoke with his Turkish counterpart, Hulusi Akar, by phone for some 30 minutes, but the Pentagon declined to give details of the call.
The Turkish Defense Ministry said, however, that Akar “told his U.S. counterpart that Turkey remains under a serious air and missile threat and that purchase of S-400 defense systems was not an option but rather a necessity."
The U.S. House of Representatives Foreign Affairs Committee said in a statement that Turkish President Recep Tayyip Erdogan "was given a very clear choice. Unfortunately, he has clearly made the wrong one," referring to the U.S. offer to sell Ankara the U.S.-made Patriot missile system instead.
The deal runs afoul of U.S. legislation -- known as Countering America's Adversaries through Sanctions Act (CAATSA) -- that targets purchases of military equipment from Russia. It sets out 12 possible retaliatory measures that President Donald Trump can choose to use against Ankara.
The measures could include such steps as banning visas and denying access to the U.S.-based Export-Import Bank or blocking transactions with the U.S. financial system and denying export licenses.
Ankara could also be excluded from the F-35 fighter jet production work and be blocked from purchasing the next-generation warplanes. Washington has already started the process of removing Turkey from the program -- halting training of Turkish pilots in the United States on the fighter jet.
Ankara plans to buy 100 of the jets for its own military’s use.
The S-400 consignment was delivered to the Murted Air Base outside the capital, Ankara, the Turkish ministry said in a statement.
The announcement and fears of economic fallout from U.S. sanctions immediately triggered a weakening in the Turkish lira to 5.7 against the dollar from 5.6775 a day earlier.
"The delivery of parts belonging to the system will continue in the coming days," Turkey's Defense Industry Directorate said separately. "Once the system is completely ready, it will begin to be used in a way determined by the relevant authorities."
Russia's Federal Service for Military and Technical Cooperation confirmed the start of the deliveries, while Kremlin spokesman Dmitry Peskov told reporters on July 12 that "everything is being done in strict accordance with the two countries’ agreements," adding that "the parties are fulfilling their obligations."
NATO has yet to react officially to the Turkish announcement, but an alliance official speaking on condition of anonymity told AFP that the 29-member bloc is "concerned about the potential consequences" of the purchase.
Trump met with Erdogan on the sidelines of last month's G20 summit in Osaka, urging him not to proceed with the purchase of Russia's defense system.
Erdogan told Trump that former U.S. President Barack Obama did not allow Ankara to buy Patriot missiles -- an equivalent of the S-400s.