By Joshua McElwee

VATICAN CITY, May 7 (Reuters) - U.S. Secretary of State Marco Rubio will meet Pope Leo at the Vatican on Thursday, in a potentially fraught encounter as President Donald Trump has continued a series of disparaging attacks on the Catholic leader over the Iran war.

Rubio, who also serves as Trump's national security adviser, was due to arrive at the Vatican's Apostolic Palace around 11:15 a.m. (0915 GMT) for the visit, the first between the pope and a Trump cabinet official in nearly a year.