Russia and Iran, keen to ease U.S. concerns over their nuclear ties, will sign in September an agreement requiring Tehran to return nuclear waste to Moscow, a Russian Atomic Energy Ministry official said on Tuesday. Russia has pressed ahead with plans to build a nuclear plant at the southern port of Bushehr in Iran despite criticism from Washington, which accuses Tehran of seeking to develop nuclear weapons under the cover of a civilian program. \"The agreement will be signed very soon, perhaps by the end of September. Last week, the Russian government instructed our ministry to sign the protocol in the nearest future,\" the official told Reuters on condition of anonymity. As soon as the protocol is signed, Russia will ship fuel to Iran for the Bushehr reactor, which will then process it to generate power and send all spent nuclear material -- which can be converted to weapons grade material -- back to Russia. The official said the document would be signed during a regular visit by a ministry delegation to the Islamic Republic in coming weeks, but the precise date of the signing was yet to be decided. U.S. Undersecretary of State John Bolton, a key U.S. arms official, is in Moscow for what is seen as an attempt to persuade Russia to halt nuclear cooperation with Iran and bring the issue of Tehran\'s nuclear ambitions before the U.N. Security Council. Iran, which says it is ready to sign the agreement with Russia, has dismissed the U.S. charges, saying it wants to develop nuclear power to satisfy a booming demand for electricity and save its oil and gas reserves for export. (Reuters)