By Humeyra Pamuk JERUSALEM (Reuters) -U.S. Secretary of State Antony Blinken sought to reassure Israeli and Arab partners convening for a rare summit in Israel on Sunday that Washington would continue to counter any Iranian threat even as he promoted nuclear diplomacy with Tehran. The issue is likely to dominate the two-day summit which will include foreign ministers from three Arab states that normalised ties with Israel even as peacemaking with the Palestinians remains stalled. Blinken pledged in parallel to work on improving Palestinian conditions. Blinken’s visit comes as some U.S. allies …