PARIS/WASHINGTON—The United States on Thursday said it was ready to talk to Iran about both nations returning to a 2015 agreement that aimed to prevent Tehran from acquiring nuclear weapons, seeking to revive a deal that Washington itself abandoned nearly three years ago. The move reflects the change in U.S. administration, with U.S. Secretary of State Antony Blinken stressing President Joe Biden’s position that Washington would return to the accord formally known as the Joint Comprehensive Plan of Action (JCPOA) if Tehran came into full compliance with the deal. Iran reacted coolly to the idea, put forward by Blinken during a video meeting with the foreign ministers of Britain, France and Germany—a group known as the E3— gathered in Paris. “If Iran comes back into strict compliance with its commitments under the JCPOA, the United States will do the same and is prepared to engage in discussions with Iran toward …