President Hassan Rouhani of Iran accused the United States on Thursday of not complying with the landmark nuclear agreement that took effect in January, and said American credibility would suffer if the accord were not honored.

In his United Nations General Assembly speech and later at an hourlong news conference, Mr. Rouhani criticized what he described as an American failure to adhere to obligations under the agreement, which relaxed many economic sanctions on Iran in exchange for verifiable pledges of peaceful nuclear work. Continue Reading.