MOSCOW — Despite chummy embraces and warm words, the leaders of Russia and France could not agree yesterday on one of the diplomatic world’s most pressing questions — whether or not Iran wants nuclear arms.

President Putin of Russia said Iran must be encouraged to make its nuclear program fully transparent, but he also said there is no proof that Tehran is seeking to build atomic weapons.

With no “objective data” showing Iran is working on nuclear arms, “we proceed from an assumption that Iran has no such plans,” Mr. Putin said after his talks with President Sarkozy of France. The talks followed a dinner Tuesday night at the Russian’s country residence.

Mr. Sarkozy, who is seeking to ratchet up international pressure on the Tehran regime, expressed hope that Mr. Putin’s visit to Iran next week would help make Iranian leaders more inclined to meet demands that it allow strong monitoring to ensure it isn’t working on atomic weapons.

“What’s very important is the willingness to cooperate — that’s the essential point. This is an issue that concerns the planet,” Mr. Sarkozy said.

America and its allies say Iran’s nuclear program is geared toward creating fissile material for atomic warheads. Tehran denies that, insisting its program is strictly for producing radioactive fuel for nuclear reactors that will generate electricity.

Tehran’s past clandestine activities and its refusal to heed a U.N. Security Council demand that it suspend uranium enrichment have heightened global fears.

The U.N. nuclear watchdog, the International Atomic Energy Agency in Vienna, Austria, says it has not detected signs of a weapons program in Iran, but is withholding judgment on what the Iranians’ goal may be.

“We have not seen any weaponization of their program, nor have we received any information to that effect — no smoking gun or information from intelligence,” the IAEA chief, Mohamed ElBaradei, said earlier this year.

Russia has opposed a push by the America, Britain, and, France for tougher sanctions against Iran, saying it will base its policies on the IAEA’s findings rather than Western accusations.

“We share our partners’ concern about making all Iranian programs transparent,” Mr. Putin said, but he added that Iran has already shown an increased readiness to do so.

“We agreed yesterday, and Mr. President [Sarkozy] confirmed it, that Iran is making certain steps toward the international community to achieve that,” Mr. Putin said.

In Washington, a State Department spokesman, Sean McCormack, said America considered Russia to be on the same page with the West in terms of Iran’s nuclear program, even if there are “some tactical differences.”