CAPITOL HILL: Acting Defense Secretary Patrick Shanahan expressed optimism on Tuesday that Turkey will cancel plans to buy Russia’s S-400 SAM system one day after the Pentagon announced the US had halted shipments of F-35 parts to Turkey in an effort to punish the NATO ally for moving ahead with the controversial purchase.

Meanwhile, the the presumptive head of European Command, Gen. Told Wolters, testified before the Senate Armed Services committee that he would recommend blocking all F-35 shipments to Turkey should Recep Tayyip Erdoğan’s government buy the S-400 later this year.

The general said he agrees with “this committee’s belief that the S-400 and the F-35 are not compatible, and if Turkey proceeds down a path to procure and operate the S-400, they should not get the F-35,” adding, “we all understand that Turkey is an important ally in the region, but it’s absolutely unsustainable to support co-location of an F-35 and S-400.”

Shanahan stuck an optimistic note when he told reporters at the Pentagon: “I expect them to be delivered.”

His confidence stems in part from what he sees as the good deal the US has offered Turkey, floating a $3.5 billion offer in December for the Patriot air defense system that would take the place of the S-400.

But Turkish officials have given no indication that they’re about to choose Patriot over its Russian counterpart, which carries a price tag of $2.5 billion. Turkish officials continue to maintain that the S-400 deal has been wrapped up, and they expect delivery to begin later this year.

Still, Shanahan said, “I am very confident in the Patriot proposal that we’ve delivered to Turkey, its availability, it’s pricing, and very importantly, the industrial participation that comes along with the Patriot system.” Turkey also stands to lose substantial industrial benefits if it is forced to leave the Joint Strike Fighter program, which will happen if the S-400 deal goes through.

But the Pentagon’s top leader said he has “had a number of conversations” with Turkish Defense Minister Hulusi Akar, “and I really think we’ll resolve this situation with our strategic partners.”

The Pentagon has not released any readouts from any of those discussions, though Shanahan and Chairman of the Joint Chiefs Gen. Joseph Dunford met in February with Akar and Gen. Yaşar Güler, chief of the Turkish General Staff, at the Pentagon.

Speaking to reporters Tuesday ahead of a two-day NATO summit in Washington, a senior US official said Turkey remains an important partner to the United States, and “our relationship is not being defined by the single issue of the S-400, but the S-400 is a deeply problematic issue for the United States.”

It doesn’t appear that Sen. Roger Wicker shares Shanahan’s optimism, telling Wolters that the Turkish insistence on buying the S-400 — which would put NATO aircraft operating in Turkey at risk — “is not what one would expect from an ally and it calls into question a lot of things that we’ve assumed from our long-term ally.”

“Turkey is a partner in the supply chain in the Joint Strike Fighter, so we not only have to look at whether we can transfer those assets to Turkey, but we also have to determine what role Turkey could play in the supply chain,” Tillis said.