The head of the U.N. atomic watchdog is urging world powers to continue dialogue with Iran to keep it in the landmark 2015 deal aimed at preventing the country from building nuclear weapons.

In his regular update to the International Atomic Energy Agency's board of governors on Monday, Yukiya Amano said he's "worried about increasing tensions over the Iran nuclear issue," adding it's "essential that Iran fully implements its nuclear-related commitments."

In its May report to member states, the IAEA said Iran has stayed within key limitations for uranium and heavy water stockpile, but said stockpiles were increasing.

The nuclear deal has been complicated by the unilateral withdrawal of the United States last year and Washington's increased sanctions, which has been taking a toll on the Iranian economy.