On May 30, the International Atomic Energy Agency (IAEA) reported that Iran had accumulated 43.3 kilograms of uranium enriched to 60 percent purity, the approximate amount necessary to build a nuclear weapon if enriched further to 90 percent. The IAEA also said that Iran had failed to provide credible responses to questions from IAEA investigators about traces of uranium found at undeclared sites within Iran. Iranian officials want the IAEA to end its investigation in June and have threatened that a failure to do so could affect ongoing negotiations over its nuclear program. According to the IAEA, Iran also continues to produce advanced centrifuges.