Moscow ? The Russian government on Friday defended its project to build a nuclear reactor in Iran but conceded that the two nations have yet to sign a pact that would return the spent nuclear fuel to Russia.

“Iran is using nuclear energy exclusively for peaceful purposes,” said Atomic Energy Minister Alexander Rumyantsev, who just returned from a four-day trip to Iran.

Russia is building a nuclear reactor in the southern Iranian port of Bushehr in a deal worth about $800 million. The United States has urged Russia to abandon the project, saying it could advance Iran’s nuclear weapons ambitions.