World powers won't get a better nuclear deal

Iran warned world powers they will not be able to negotiate a better deal than the landmark 2015 nuclear agreement, as the United States vowed the Islamic Republic will never acquire an atomic weapon.

Tehran threatened on Monday to restart deactivated centrifuges and ramp up its enrichment of uranium to 20 percent purity as its next potential big moves away from the agreement that Washington abandoned last year.

The latest war of words came the same day that Iran began enriching uranium to 4.5 percent, breaking the limit set in the 2015 agreement sealed under former president Barack Obama.