Turkish President Recep Tayyip Erdogan said on Tuesday he told US President Donald Trump during talks in Washington last week that Turkey would not give up on the Russian S-400 missile defence systems it procured this year despite protests from its NATO ally.
Erdogan and Trump held talks at the White House to overcome mounting differences between the allies.
Washington has said the S-400s pose a threat to its F-35 stealth fighter jets and has suspended Turkey from the jet programme, where it is a buyer and manufacturer.
It has also warned of US sanctions over the deal, but has yet to impose them, Reuters reported.
Speaking to members of his AK Party in parliament, Erdogan also said he had told Trump that if the US maintained its "uncompromising stance" on the F-35s, Turkey would have to
seek alternatives to meet its medium-term defence needs.
Also, the Turkish president said Ankara would continue to fight against the Syrian Kurdish YPG, even though Turkey is aware that the US support for them will not end immediately.
Turkey views the YPG as a terrorist group linked to Kurdish militants waging an insurgency on Turkish soil, and has launched three offensives in northern Syria against them.