(CNN) The Pentagon has halted the delivery of equipment related to the F-35 jet to Turkey due to Turkey's decision to purchase the Russian-made S-400 missile system.

"Pending an unequivocal Turkish decision to forgo delivery of the S-400, deliveries and activities associated with the stand-up of Turkey's F-35 operational capability have been suspended while our dialogue on this important matter continues with Turkey," Lt. Col. Mike Andrews told CNN in a statement.

"We very much regret the current situation facing our F-35 partnership, but the DoD is taking prudent steps to protect the shared investments made in our critical technology," he added.

The news of the delivery suspension was first reported by Reuters.

The announcement comes as the Turkish Foreign Minister heads to Washington for a ministerial meeting marking the 70th anniversary of NATO.

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