US Secretary of State Hillary Rodham Clinton travels to Russia on Monday hoping to win Moscow's backing for a strong stance on Iran's nuclear program and looking for progress on a new arms control pact. American officials say Iran will be at or near the top of Clinton's agenda when she meets Russian President Dmitry Medvedev and Foreign Minister Sergey Lavrov on Tuesday. She plans to push for Russian support for new sanctions on Iran if it doesn't comply with demands to prove its nuclear program is peaceful. On Sunday, in London on the second leg of her current five-day overseas tour, Clinton warned Iran that the world "will not wait indefinitely" for proof it is not trying to develop atomic weapons. She said a recent meeting in Geneva in which Iran and six world powers resumed nuclear talks was "a constructive beginning, but it must be followed by action" from the Iranians. Iran insists it has the right to a full domestic nuclear enrichment program that it maintains is only for peaceful purposes, such as energy production. Russia and China have long balked at imposing new sanctions on Iran if it fails to come clean about its suspect nuclear program, although Medvedev hinted the Russian position might be shifting after Teheran disclosed a previously secret uranium enrichment site near the holy city of Qom. But US officials believe it will be a hard sell to convince the Russians on fresh penalties since Iran agreed to allow UN inspectors to visit the Qom site and has agreed, in principle, to send most of its low-enriched uranium to Russia for reprocessing. Iran agreed to allow inspections of the Qom site following the Geneva talks between Iran's chief nuclear negotiator and diplomats from the US, Russia, China, Britain, France and Germany. The Iranians were given time to decide whether to accept a package of incentives in exchange for Iran's compliance with international demands to suspend its uranium enrichment or face new sanctions. The Obama administration is anxious not to let up on the pressure and Clinton will be looking for Russian expressions of support for sanctions and other penalties should Iran continue to refuse by the end of the year, the officials said. As Clinton left Washington on Friday for Switzerland, Britain, Ireland and Russia, Medvedev said his government does not want to see any more nations develop nuclear weapons, signaling that Moscow shares US concerns about Iran. But he said nothing about potential sanctions. In addition to Iran, Clinton will bring a wide array of other issues to Moscow, including arms control, missile defense and cooperation on convincing North Korea to abandon nuclear weapons, the officials said. Negotiators from the two countries are racing to reach agreement on a successor to the 1991 Strategic Arms Reduction Treaty, or START I, and Clinton wants to underscore the urgency of the talks, they said. She also will explore possible cooperation on missile defense following President Barack Obama's decision not to proceed with Bush-administration plans to base such a system in eastern Europe. Russia had vehemently opposed those plans and has welcomed Obama's new approach. Though the Kremlin is pleased with the move, it has pushed for a link between missile defense and the START talks. Russian and US diplomats were to hold consultations about missile defense on Monday prior to Clinton's arrival. Clinton will also join Lavrov in chairing a meeting of a commission set up by Obama and Medvedev to improve cooperation and coordination on a variety of matters, including Afghanistan.