WASHINGTON (Reuters) - The United States on Thursday imposed sanctions on Chinese and Emirati companies and a network of Iranian firms that help export Iran's petrochemicals, a step likely aimed at raising pressure on Tehran to revive the 2015 Iran nuclear deal.

       "The United States is pursuing the path of meaningful diplomacy to achieve a mutual return to compliance with the Joint Comprehensive Plan of Action," Under Secretary of the Treasury for Terrorism and Financial Intelligence Brian Nelson said in a statement, referring to the 2015 agreement.

       "Absent a deal, we will continue to use our sanctions authorities to limit exports of petroleum, petroleum products, and petrochemical products from Iran," Nelson said. "The United States will continue to expose the networks Iran uses to conceal sanctions evasion activities."

       The nuclear pact seemed near revival in March but talks were thrown into disarray partly over whether Washington might remove the Islamic Revolutionary Guard Corps, which controls armed and intelligence forces that Washington accuses of a global terrorist campaign, from its the U.S. Foreign Terrorist Organization list.

       (Reporting by Arshad Mohammed, Daphne Psaledakis and Doina Chiacu; Editing by Paul Grant and Daniel Wallis)