Here is Trump's tweet:
Adelson, 82, owner of the Las Vegas Sands Corp., has said that he likes the Florida senator, but officials have said that he has made no firm decision on who to support.
Republican hopefuls turned out in force in April to court Adelson's support during the spring meeting of the Republican Jewish Coalition at Adelson's Venetian Hotel.
He has been seeking a pro-Israel candidate with broad enough appeal to win the White House next year. Adelson is the No. 12 on the Forbes list of the world's richest people.
Trump is financing his primary bid. He has attacked both Rubio and former Florida Gov. Jeb Bush as "low energy."