MOSCOW — Russia and NATO-member Turkey are in talks over the possibility of creating a new fighter jet, Russian government officials said Wednesday, a step that could further challenge the United States and Ankara’s standing in the Western military alliance.

The move came as President Vladi­mir Putin hosted his Turkish counterpart, Recep Tayyip Erdogan, at a major Russian aviation show on the outskirts of Moscow, a meeting which served mostly as a showcase for the two leaders’ burgeoning partnership.

The two sides held “technical consultations” on the joint creation of a fighter jet and “initial talks” on developing a Turkish fighter aircraft, Russian media cited officials from Russia’s Federal Service for Military-Technical Cooperation as saying. The body reports directly to Putin.

No additional details were provided. The discussions, though tentative, are likely to raise further alarms in Washington, which has strenuously protested against Turkey’s recent purchase of the S-400 Russian missile defense system.

U.S. officials worry Russia could use the S-400s in Turkey to gather intelligence on the United States’ F-35 fighter jet. In response, the United States has canceled Turkey’s participation in the production and purchase of the F-35 stealth aircraft.

Meanwhile, U.S. House Foreign Affairs Committee members urged President Trump on Tuesday to level further sanctions on Turkey for the purchase.

Turkey is already developing its own stealth fighter, which could be operational as early as 2025, Turkish officials have said.

In Moscow, Erdogan and Putin also discussed cooperating in the field of “electronic warfare” at a moment of heightened vigilance in the West over Russian cyberattacks.

The optics suggested Turkish-Russian relations were growing warmer. In a video clip that went viral, Putin bought himself and Erdogan ice cream cones. (The Russian leader chose chocolate, while Erdogan preferred vanilla.)

The pair then admired Russia’s newest fighter jet, the Sukhoi Su-57, which was unveiled at the show, with Erdogan getting a peak inside the cockpit. Erdogan joked about purchasing the Su-57, but stopped at that.

The Russian space agency Roscosmos even offered to send a Turkish astronaut to the International Space Station.

Behind the scenes, there was no sign that the two countries had resolved their disagreements over the war in Syria.

Russia, the main military backer of Syrian President Bashar al-Assad, has supported Syria’s months-long offensive in the country’s northern Idlib province, along the border with Turkey.

The Syrian advance has killed Turkish soldiers stationed as observers in Idlib and has sent hundreds of thousands of displaced Syrians toward the Turkish border, raising fears in Ankara of a new influx of refugees.

Earlier this month, a Turkish military convoy was bombed in Idlib, in an attack that Turkey partly blamed on Russia.

At a joint news conference Tuesday, Erdogan and Putin did not attempt to paper over their diverging views of the violence in Idlib.

Erdogan called the Syrian government’s attacks, which have killed hundreds of civilians, “unacceptable,” adding that they were “strengthening radical elements.”

Putin acknowledged an “escalation of the violence” but blamed it on “radical elements” attacking Russian bases and the Syrian population as a whole.

Erdogan’s courting of Russia has laid bare the rapid decline of Turkey’s relationship with the United States, which is from a litany of perceived slights and grievances.

The two governments have argued over the White House’s refusal to extradite a Turkish cleric blamed by Erdogan’s government for helping fuel a failed coup in 2016. Turkey also objects to U.S. support for a Syrian-Kurdish force allied with the Kurdistan Workers’ Party, or PKK, which has fought a long insurgency against Turkey.

“The root cause of the problem is that both America and Turkey see each other as a fundamentally destabilizing actor in the Middle East,” Aaron Stein, the director of the Middle East Program at the Foreign Policy Research Institute in Philadelphia, wrote earlier this month in an essay about the tortured negotiations between Ankara and Washington over policy in Syria