article_snippet.sent: The world powers involved in the talks with Iran were the United States, Russia, China, France, the United Kingdom and Germany.
article_snippet.sent: For the United States and Iran, two countries with a long history of strained relations, the negotiations took on an added significance.
article_snippet.sent: But U.S. leaders were still talking tough, even as U.S. leaders praised the agreement.
article_snippet.sent: We have serious differences with the United States," Foreign Minister Javad Zarif said after the deal's framework was announced, noting that "mutual mistrust" had been a serious problem in the talks.
article_snippet.sent: Negotiations between Iran and the five permanent members of the U.N. Security Council -- China, France, Russia, the United Kingdom and the United States -- plus Germany began in 2006 and have had a tortured history.
article_snippet.sent: Meanwhile, as talks dragged on, the United States, the European Union and others imposed sanctions on Iran, provoking resentment among Tehran's leaders, who called sanctions on Iran a crime against humanity.
article_snippet.sent: U.S. leaders also were divided over an agreement.
article_snippet.sent: Democrats denounced the sending of such a letter to foreign leaders as an unprecedented intervention in negotiations between the administration and another country.