WASHINGTON, June 13 (Reuters) - The U.S. State Department said on Thursday that Washington and its allies were prepared to continue to increase pressure on Iran if Tehran does not cooperate with the U.N. nuclear watchdog.

Iran has rapidly installed extra uranium-enriching centrifuges at its Fordow site and begun setting up others, a U.N. nuclear watchdog report said earlier in the day. The State Department said the report showed that Iran aimed to continue expanding its nuclear program "in ways that have no credible peaceful purpose."

(Reporting by Kanishka Singh in Washington; Editing by Leslie Adler)