Reporting from Moscow — Secretary of State Hillary Rodham Clinton had barely arrived in Moscow for nuclear arms and Mideast talks when tensions over Iran flared up publicly Thursday.
Meeting reporters alongside her Russian counterpart, Foreign Minister Sergei Lavrov, Clinton reproached Moscow for building and fueling a nuclear power plant in Iran. Tehran is not entitled to generate nuclear energy for civilian purposes, Clinton said pointedly, until it puts to rest suspicion that it is secretly pursuing a nuclear weapons program.
Earlier Thursday, Prime Minister Vladimir Putin announced that the Russian-built reactor would begin to generate electricity in Iran as early as this summer.
"If [Iran] reassures the world, or if its behavior is changed because of international sanctions, then they can pursue peaceful, civil nuclear power," Clinton said. "In the absence of these reassurances, we think it would be premature to go forward with any project at this time because we want to send an unequivocal message to the Iranians."
At her side, Lavrov held his ground.
"Russia is involved, and this project will be completed," Lavrov said. "This nuclear power plant will finally be launched, and it will generate electricity."
Lavrov argued that the plant is crucial to the International Atomic Energy Agency's presence in Iran, providing a foothold for monitoring whether Tehran complies with nonproliferation requirements.
The clash underlined lingering and sticky disagreements between the United States and Russia over how best to confront Iran. The Obama administration badly needs Russian backing in order to pursue more aggressive action against Iran and has been pressing Moscow for support.
There was some speculation recently that those efforts were beginning to bear fruit, as Russian officials sounded bursts of harder rhetoric against Iran's nuclear program.
But Russia, which maintains close business and diplomatic ties with Iran, has adroitly sidestepped pressure to publicly commit itself to tougher sanctions.
Russia and China, which also has resisted taking a harder approach with Iran, are permanent members of the U.N. Security Council and can thus veto any U.S.-backed resolution imposing additional sanctions on the Islamic Republic.
The reactor construction at Bushehr has pricked at U.S.-Russian relations for years, as Moscow built the power plant and began to send Iran nuclear fuel.
In 2007, Russian officials said Iran had lagged in its payments and that the plant opening might be delayed. Rumors swirled that U.S. pressure had finally persuaded Moscow to drag its feet.
But the project has since regained its momentum. Putin, who views nuclear power as a promising industry for Russia to pursue around the world, appears eager to see the plant generating power.
Clinton was not originally scheduled during her two-day visit to meet with Putin, who is widely seen as Russia's top ruler. But a meeting between the two was hastily added to the Friday agenda.
Clinton is also scheduled to hold talks with Russian President Dmitry Medvedev, as well as representatives of the United Nations and the European Union, who along with the United States and Russia constitute the so-called quartet of Mideast peace sponsors. The quartet is to hold talks Friday aimed at prodding Israelis and Palestinians back to peace talks.
In the background of Clinton's Moscow trip, U.S. and Russian negotiators are still struggling to finalize an agreement on nuclear arms control. The talks have turned into something of an embarrassment, with both sides repeatedly saying the agreement is close to completion as nearly a year slipped away.