WASHINGTON - US President Donald Trump is expected to announce soon that he will decertify the landmark international deal to curb Iran's nuclear program, a senior administration official said on Thursday, in a step that potentially could cause the 2015 accord to unravel.

The official, speaking on condition of anonymity, said Trump is also expected to roll out a broader strategy on Iran that would be more confrontational.

Trump, who has called the pact an "embarrassment" and "the worst deal ever negotiated," has been weighing whether it serves United States security interests as he faces an Oct 15 deadline for certifying that Iran is complying with its terms.