President Trump and Turkish President Recep Tayyip Erdoğan quietly sought to arrange a meeting between senior U.S. and Iranian officials in Istanbul this week amid Israel's escalating war with Iran. But the effort collapsed when Iran's supreme leader — in hiding due to fears of assassination — couldn't be reached to approve it, according to three U.S. officials and a source with direct knowledge of the matter. -snip- Behind the scenes: Trump received a phone call from Erdoğan on Monday while meeting with G7 leaders in Canada. Erdoğan proposed hosting a meeting in Istanbul the next day between U.S. and...