Pentagon report on Turkey's F-35 program delivered to Congress

The US Defense Department has delivered a report to Congress detailing implications of Turkey receiving 100 F-35 fighter jets, five people familiar with the report said, removing a key hurdle to concluding the deal.

Turkey's planned purchase of the Russian-made S-400 missile defense system has raised concerns in the West, since it could be used to give Moscow deep insight into the vulnerabilities of the most advanced US warplane at a time of tension between the two powers, experts have said.

Ellen Lord, the Pentagon's chief arms buyer, told Reuters in an interview that Turkey's plans to buy the S-400 system were "extremely problematical" and numerous.

US officials had discussed the issue with Ankara, but there were no signs that Turkey had changed its mind about buying the Russian system.

The United States has for years offered Turkey an alternative missile...