The United States said Tuesday that a new report by the UN International Atomic Energy Agency (IAEA) reinforces US concerns about Iran's nuclear program. "The IAEA is documenting that Iran continues to fail to cooperate with IAEA," State Department spokesman Philip Crowley told reporters. The report "underscores our concern about ongoing Iranian enrichment, the continued construction of a heavy-water research reactor, concerns about cooperation with the IAEA, access of inspectors to key sites," he said. The UN watchdog said Monday that Iran is hampering a long-running investigation into its controversial nuclear drive by vetoing the nomination of certain UN inspectors. It also said that a number of its seals had been broken on equipment at Iran's main uranium enrichment plant in Natanz. Nonetheless, Crowley said the United States still believes that the fourth round of UN Security Council sanctions adopted in June, coupled with measures taken by individual governments, "is having an impact on the ground in Iran."