TEHRAN, Sept. 23 (Xinhua) -- Iran's Supreme Leader Ali Khamenei on Tuesday warned against nuclear negotiations with the United States under the present circumstances, saying it will not serve Iran's national interests. Khamenei listed some of the U.S. hostile actions against Iran over the past years, saying negotiation with the U.S. on Iran's nuclear issue as well as other matters would be an "absolute dead end." Iran signed a nuclear deal with world powers in July 2015, agreeing to put some curbs on its nuclear program in return for the removal of sanctions. The U.S., however, pulled out of the deal in May 2018 and reimposed sanctions on Iran, prompting Tehran to scale back its commitments under the deal. In April, Iran and the U.S. began indirect talks on Tehran's nuclear program and the removal of U.S. sanctions.