May 25, 2017 0501 GMT
Trump was going to renew the sanctions waivers that were issued under the deal later on Wednesday, unnamed US officials told Reuters.
Under the deal, known as the Joint Comprehensive Plan of Action (JCPOA), Iran agreed to limit parts of its peaceful nuclear program in exchange for removal of all nuclear-related sanctions imposed by the US.
Trump’s predecessor Barack Obama renewed the waivers days before he left the White House in January. Some of the waivers would expire if Trump refuses to extend them this week.
The decision poses a major challenge for Trump, who has been critical of the deal.
As a candidate in the 2016 presidential election, Trump frequently criticized the JCPOA as “the worst deal ever negotiated,” but offered conflicting opinions on whether he would try to scrap it, renegotiate its terms or keep it in place.
After accusing Iran of “not living up to the spirit” of the deal, the new Republican president said in April that his administration was analyzing the JCPOA and would “have something to say about it in the not-too-distant future.”