 By Humeyra Pamuk, Patricia Zengerle and Mike Stone WASHINGTON Reuters -The Biden administration has told Congress it is preparing the potential 20 billion sale of F-16 fighter jets to Turkey, sources familiar with the matter said on Friday, sparking an immediate objection from a senior U.S. lawmaker who has long opposed the deal. The State Department sent the informal notice to Congress on Thursday, three sources said, informing committees overseeing arms sales in the Senate and House of Repr... 