ANKARA (Reuters) - Turkey is not distancing itself from the NATO alliance by buying Russian S-400 missile defense systems, Turkish Defence Minister Hulusi Akar said on Friday, adding that Ankara should not be excluded from the F-35 jet project over the purchases.

FILE PHOTO: Turkey's Hulusi Akar, when he was chief of the general staff, during the EFES-2018 military exercise near the Aegean port city of Izmir, Turkey May 10, 2018. REUTERS/Osman Orsal/File Photo

Turkey and the United States, NATO allies, have been at odds over Ankara’s move to buy the Russian S-400s, which Washington says are not compatible with NATO systems and may threaten the Lockheed Martin F-35 fighter jets, of which Turkey is a prospective buyer and partner in production.

In an interview with broadcaster NTV, Akar said that excluding Turkey from the F-35 project would put “very serious” burdens on the other partners in the project.

“There is no clause saying ‘you will be excluded if you buy S-400s’ in this partnership. Excluding us just because any one country wants so would not be in line with justice, laws or rights. This should not happen,” Akar said.

He said Turkey was trying to explain to the United States and other partners in the F-35 project that the S-400s would not pose a threat to the jets, and added that Ankara had taken measures to prevent that.

In his strongest challenge yet to warnings that Turkey may be removed from the F-35 project, President Tayyip Erdogan said on Tuesday that the project would collapse if Turkey did not participate.

In a sign of how Washington was preparing for contingencies if Turkey was dropped from the F-35 program, acting Defense Secretary Patrick Shanahan said on Friday he met with Lockheed Martin and United Technologies Corp. last week to go over plans.

“I want airtight plans that have near-zero execution risk so we can flawlessly deliver on all the other F-35s to our other customers,” Shanahan said.

Lockheed is the prime contractor on the jet, while United Technologies makes the jet’s engine.

In March Reuters reported Washington was exploring whether it can remove Turkey from production of the stealth fighter jet, angered by Ankara’s refusal to back down from its planned purchase of the Russian missile system.

While Washington has warned of potential U.S. sanctions if Ankara pushed on with the S-400 agreement, Turkey has said it would not back down from the deal.

Instead, Turkey has proposed to form a working group with the United States to assess the impact of the S-400s, but says it has not yet received a response from U.S. officials.

Akar said on Friday Turkey was still evaluating the latest U.S. offer to sell Raytheon Co. Patriot systems, which he said was more positive than Washington’s previous offers.

Turkey said two weeks ago it expected U.S. President Donald Trump to use a waiver to protect it against penalties over the S-400s, after U.S. Secretary of State Mike Pompeo said Ankara could face retribution for the deal under the U.S. Countering America’s Adversaries Through Sanctions Act (CAATSA).