The Joe Biden administration did not threaten additional sanctions after reports that Turkey plans to receive a second batch of Russian S-400 missile defense systems, Defense News reported.

Turkey originally purchased the S-400 in 2017, which led to a crisis in its relations with the United States. As a result of the deal, the Trump administration excluded Turkey from the F-35 program and then imposed sanctions on the country's defense industry organization and its leaders. The United States fears that the powerful S-400 radar system will allow Russia to spy on the advanced F-35 fighter jet.

But this time, the reaction in the United States has been relatively muted. In a press briefing, State Department spokesman Ned Price urged Turkey not to engage with the Russian defense sector.

Price said the point they have consistently made across the board is that Russia's brutal and unjustified war against Ukraine makes it vital, now more than ever, that all countries avoid deals with the Russian defense sector. They will have to wait and see what happens, but they're not aware of any new developments on that issue.

Price declined to answer whether the purchase of the new batch would make him reconsider plans to sell F-16 fighter jets to Turkey.

Earlier, TASS quoted Dmitri Shugayev, head of Russia's Federal Service for Military-Technical Cooperation (FSMTC), as saying that a contract had been signed to supply Turkey with a second regiment of S-400 air defense missile systems.

Sources in the Turkish defense ministry hastened to deny Russia's statements about signing an additional contract, noting that the second S-400 regiment was part of the original agreement.

Turkish sources told Defense News that there may be an agreement with Russia to produce some S-400 components for the second regiment domestically.

Turkey's difficult balance between the West and Russia has become even more complicated since the war in Ukraine. The strongest sign of warming in Turkish-US relations came at the end of June, when Turkish leader Recep Tayyip Erdoğan dropped his objections to Finland and Sweden joining NATO. Then US President Joe Biden expressed support for selling F-16s at the NATO summit in Madrid in June.

A delegation from Ankara arrived in the U.S. on Monday for the fourth round of technical talks with Washington on a potential F-16 deal, Anadolu reported.

Turkey has requested the purchase of 40 Lockheed Martin Block 70 F-16 fighter jets for $6 billion. It is also seeking a separate $400 million sale to upgrade its current F-16 jets with new missiles, radar and electronics.

Senate Foreign Relations Committee Chairman Bob Menendez has threatened to block the F-16 sale because of Turkey's continued possession of S-400s, its violations of Greek airspace and Cypriot waters in the eastern Mediterranean, human rights abuses and ongoing attacks on US, backed Kurdish rebels in northeastern Syria.

Eric Edelman, a former US ambassador to Turkey and senior Pentagon official, said he believes the S-400 deal will hamper efforts to build relations between Turkey and the United States. To put it mildly, it will complicate the Biden administration's efforts to sell F-16s to Turkey and anger Turkey's growing legion of detractors on Capitol Hill, Edelman said.

Jim Townsend, the Pentagon's top official for Europe and NATO under the Obama administration, said he doubts the S-400 deal was done without advance warning to the U.S. from Turkey. He suggested it was part of an international grain deal. He added that the restrained U.S. response to the announcement is key. If they are not shouting from the rostrum, they probably knew about it, Townsend said.