Turkey’s presidential spokesman Ibrahim Kalin said on Thursday he spoke on the phone with President Donald Trump’s national security advisor John Bolton to discuss a letter sent by the Pentagon about Ankara’s removal from the F-35 jets program, reports Reuters.

Kalin said he hoped the Pentagon would abandon its current attitude toward Turkey, which he said could permanently damage ties between the two NATO allies.

Kalin also said Erdogan was set to meet with Russian President Vladimir Putin at the end of June during the G20 meeting in Japan.