The head of the International Atomic Energy Agency warned Thursday that the "space for negotiation and diplomacy ... is getting smaller" over Iran's advancing atomic program as wars in the Mideast rage on and as President Donald Trump will return to the White House.

Rafael Mariano Grossi of the IAEA was visiting Tehran in an effort to restore his inspectors' access to Iran's program and answer still-outstanding questions over it, as he has on previous trips with limited success since Trump unilaterally withdrew the U.S. from the Islamic Republic's nuclear deal with world powers.