washington president donald trump middle east peace negotiator jason greenblatt return israel continue peace track president meet israeli prime minister benjamin netanyahu palestinian president mahmoud abbas last week new york white house official say sunday president trump productive meet prime minister netanyahu president abbas unite nations always say un would focus peace conversations conversations would happen separate track official say statement greenblatt follow-up meet advance private trip region family sukkot meet part administration quiet steady discussions toward peace say sukkot jewish holiday trump aide greenblatt return israel peace talk official