Washington, Oct 13: US President Donald Trump will on Friday announce his decision on whether to certify the 2015 multilateral accord on restricting Iran's nuclear activities, the White House said. White House Spokeswoman Sarah Sanders told reporters on Thursday that Trump would discuss the nuclear treaty in the course of an address on Washington's overall strategy toward Iran, Efe news reported. The US President has until October 15 to make a formal recommendation to Congress, taking into account both Iran's compliance with the terms of the accord and the question of whether the agreement is in the US national interest. Under the document that Iran signed with the US, Russia, China, France, Britain and Germany, Tehran accepted limitations on its nuclear activities in exchange for the lifting of economic sanctions. Trump, a long-time foe of the pact, has kept up a stream of harsh rhetoric against Iran since taking office in January. A decertification by Trump would open a 60-day review in the US Congress, which could decide to re-impose sanctions on Iran. The President contends Tehran is violating the "spirit" of the nuclear agreement by continuing to carry out tests of ballistic missiles and accuses Iran of being a state sponsor of terrorism, even as Iranian forces battle the Islamic State (IS) militants in Syria and Iraq. Iran is united in defence of the nuclear accord, President Hassan Rouhani said on Wednesday. Tehran flatly rejects re-negotiating the pact, an idea that likewise seems to have no support among the other signatories, who have indicated that they would not re-impose sanctions on Iran regardless of what Washington does.