S-400 system
S-400 systemReuters

US officials said on Monday that Washington has stopped delivery of F-35 fighter jet parts to Turkey in response to Ankara's decision to move ahead with the purchase of a Russian surface-to-air missile system, The Associated Press reported.

The officials spoke anonymously to discuss the decision before it was announced.

Ankara's push to buy the systems from Moscow has caused tensions with the US, its NATO ally.

Military experts are concerned that the deployment of S-400s would put the security of allied weapon systems, particularly F-35 aircraft and radar facilities, in danger.

The US believes the S-400 sale is part of Russian efforts to disrupt the alliance amid Western concern over Erdogan's burgeoning relationship with Russian President Vladimir Putin.

The US has been warning Turkey for months that buying the Russian S-400 system would jeopardize its planned purchase of the advanced fighter aircraft. The halt in the delivery of parts and manuals is the first step toward ending the actual aircraft sale.

A top US general said last month he would recommend that the United States withhold delivery of F-35 fighter jets to Turkey if Ankara goes through with the purchase of the Russian S-400 air defense system.

Monday’s move comes just days after Turkey's foreign minister said his country was committed to a deal to buy the Russian system and was discussing delivery dates.

In January, Turkey rejected a US offer to cancel its purchase of S-400 missiles from Russia. This came after a spokesman for President Recep Tayyip Erdogan made clear that Turkey’s purchase of US missiles will not affect its deal to acquire rival S-400 missiles from Russia.

Erdogan insisted last month that Turkey's deal to buy Russian S-400 missile defense systems had "nothing to do" with the security of the US.