U.S. and European diplomats went on a flurry of calls in the hours after U.S. President Donald Trump offered on Monday to join prospective Ukraine-Russia talks later this week, trying to find a path that would bring an end to the war in Ukraine. Trump's surprise offer to join the talks on Thursday in Istanbul came a day after Ukrainian President Volodymyr Zelenskiy, in a fresh twist to the stop-start peace talks process, said he would travel Turkey and wait to meet President Vladimir Putin there. -snip- Russian Foreign Minister Sergei Lavrov held talks late on Monday with his Turkish...