F-35 program on track to replace Turkey, say Pentagon officials
Trump has not yet decided whether to impose congressional sanctions on Turkey for the S-400 purchase
Trump to Erdogan: “We understand each other’s country”
Erdogan tried to persuade Trump to continue the process of buying the F-35s, but also to stop the prosecution against the Turkish state-owned Halkbank executive
Trump sent second letter to Erdogan threatening sanctions over S-400s
Letter set out US conditions for resolving crisis over Russian-made missiles ahead of White House meeting, but Turkish president was not convinced, sources say