Rafael Grossi, head of the International Atomic Energy Agency, the U.N. nuclear watchdog, says the window of opportunity to diplomatically engage with Iran is beginning to "shrink."

Iran has long accused Israel of targeting its nuclear program through covert operations. Israeli officials, in turn, have hinted at potential strikes on Iran's nuclear sites. This exchange of threats that has intensified amid ongoing hostilities between the two nations since Israel's attacks on Hezbollah, a long-standing ally.

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.