By KAREN DEYOUNG AND KAREEM FAHIM | The Washington Post | Published: March 14, 2021 WASHINGTON — The United States is willing to sit down with Iran "tomorrow" and jointly agree to full compliance with the nuclear accord they and five other world powers signed in 2015, according to a senior Biden administration official. "We've made clear that we're not talking about renegotiating the deal," the official said of the agreement that curbed Iran's nuclear program in exchange for lifting U.S. and other sanctions. Iran has made equally clear that it shares the goal of going back to the terms of the agreement as they were before President Donald Trump pulled out of it. Trump reinstituted the sanctions and added what Biden officials estimate were at least 1,500 new ones. In response, Iran reactivated key elements of the program the United States and others say could produce nuclear weapons. Iran denies any such ambition.