Washington, Aug. 18 -- Vladimir Putin agreed at his summit with President Donald Trump that the United States and its European allies could offer Ukraine a security guarantee resembling NATO's collective defence mandate as part of an eventual deal to end the war, a US official said Sunday. Trump envoy Steve Witkoff, who took part in the talks Friday at a military base in Alaska, said it "was the first time we had ever heard the Russians agree to that" and called it "game-changing." Witkoff offered few details on how such an arrangement would work. But it appeared to be a major shift for Putin.P10...