That would be King Abdullah of Jordan.
Trump's "promise" was nothing more than a campaign tactic aimed at fending off attacks from his Republican rivals during the primary season last year. He had previously promised a more even-handed approach to the Israel-Palestine dispute, which was almost certainly his own instinct on the matter before politics came into play.
It was reported that Israel wanted him to not make a move on Jerusalem yet.
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Jordan will not likely exist as a nation by the end of this year.