President Trump said Tuesday he would walk away from the Iran nuclear agreement, a decision he took after concluding that the deal has emboldened Iran and prevents the U.S. from keeping Iran from developing a nuclear weapon.

“I am announcing today that the United States will withdraw from the Iran nuclear deal,” Trump said in a White House press conference.

“We will be instituting the highest level of economic sanction,” he added before signing a declaration to impose those sanctions. “Any nation that helps Iran in its quest for nuclear weapons could also be strongly sanctioned by the United States.”

Tuesday’s announcement came a little more than six months after the president informed Congress he would not re-certify the agreement, which he had long hammered as an insufficient insurance policy against Iran’s weapons development program. Trump’s biggest grievance with the Obama-era deal has always been its so-called “sunset clause,” a provision that allows key limitations on Iran’s use and development of new technologies for uranium enrichment to be phased out beginning in 2025.

Israeli officials in particular had urged Trump to scrap the deal in the weeks leading up to his announcement, arguing that the current structure forces the U.S. and its allies to prepare for a day when Iran has nuclear weapons because of the agreement’s expiring constraints, according to a national security source close to the White House.

U.S. officials began working closely with their European counterparts in January to make improvements to the nuclear deal, known as the Joint Comprehensive Plan of Action, so Trump might be less inclined to withdraw from it entirely. But Secretary of State Mike Pompeo reportedly informed France, Germany and the United Kingdom late last week that the president was dissatisfied with the proposed changes and planned to take unilateral action.