Russian Prime Minister Vladimir Putin said Thursday that Iran's new Russian-built nuclear power plant will begin operating this summer, even as the United States called for Russia to delay the startup.In apparent response, US Secretary of State Hillary Rodham Clinton – in Moscow on an official trip – urged Russia not to start up the plant until Teheran proves that it's not developing atomic weapons.But Russian Foreign Minister Sergey Lavrov, at a joint news conference with Clinton, immediately stepped in to say that Russia would put the reactor online.RELATED:Clinton: US pressing for talks between Israel, PAUS envoy urges China to help on IranPutin, who is expected to meet with Clinton Friday, was on a trip to southern Russia when he said Moscow was committed to starting operations at the Iranian atomic power plant."The first reactor at Iran's nuclear power plant in Bushehr is to be launched already in the summer," Putin said.He didn't mention an exact startup date or add any other details during his meeting with nuclear officials in the city of Volgodonsk. Both Putin and President Dmitry Medvedev are expected to meet with Clinton Friday. Russia signed a $1 billion contract in 1995 for building the Bushehr plant, but it has dragged its feet on completing the project for years.Moscow has cited technical reasons for the delays, but analysts said Moscow had used the project to press Teheran to ease its defiance over its nuclear program.Some Iranian lawmakers have accused Russia of delaying the project under Western pressure.Later, Clinton urged Russia to postpone the plant startup until Iran proves it is not trying to build nuclear weapons."If it reassures the world, or if its behavior is changed because of international sanctions, then they can pursue peaceful, civil nuclear power," Clinton said when asked about Russian intention to start Bushehr."In the absence of those 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," she said at a briefing following her talks with Russian Foreign Minister Sergey Lavrov.Lavrov immediately responded that Russia still intends to start up the plant."The project will be completed, and now we have entered a final phaseof technological preparations," he said, adding that the plant has beenclosely supervised by the International Atomic Energy Agency. Lavrov said that the Bushehr project is essential for persuading Iranto cooperate with the IAEA and fulfill its obligations underinternational nuclear nonproliferation agreements.Russia has walked a fine line on Iran for years. It is one of the sixpowers leading international efforts to ensure Iran does not develop anatomic bomb.But it also has tried to maintain friendly ties with the IslamicRepublic, a regional power close to Russia's vulnerable southern flank.