President Vladimir Putin said Wednesday that Iran must be encouraged to make its nuclear program fully transparent, but also underscored there is no proof it is pursuing a nuclear weapons program.

"We are sharing our partners' concern about making all Iranian programs transparent," Putin said at a news conference after talks with visiting French President Nicolas Sarkozy. "We agreed yesterday, and Mr. President confirmed it, that Iran is making certain steps toward international community to achieve that."

Putin is to make his first visit to Iran early next week for a summit of Caspian Sea nations.

Sarkozy said Putin's trip to Tehran could encourage Iran to be more cooperative. "After the trip, there could be a will to cooperate -- that is essential," he said.

Russia has opposed the U.S.-push for tougher sanctions against Iran and called for more checks and inspections of Iranian facilities by an international nuclear watchdog.

"We have worked cooperatively with our partners at the United Nations Security Council, and we intend to continue such cooperative work in the future," Putin said.

But he said with no "objective data" showign Iran is developing nuclear weapons, "we proceed from an assumption that Iran has no such plans."

Sarkozy has hardened France's stance on Iran in recent months, shifting closer to the United States in his insistence on tough U.N. Security Council sanctions and even his mention of the possibility of war. While the U.S. and European nations are pressing for greater sanctions, Russia and China have resisted.