The United States and Russia may sign a new nuclear arms reduction agreement in early April, after a previous treaty expired in December, Secretary of State Hillary Clinton said Friday. 'As we speak, our negotiations in Geneva are wrapping up the final elements of the START treaty,' Clinton said in an interview with Bloomberg TV in Moscow. 'We hope to have a signing ceremony between President Medvedev and President Obama in early April.' Clinton later told reporters that only 'technical issues' remain to be resolved. The two governments are trying to agree on the first new treaty in two decades to reduce the number of nuclear weapons and the air and sea vehicles used to deliver them. Presidents Dmitry Medvedev and Barack Obama called in July for a reduction of the two countries' arsenals to between 1,500 and 1,675 deployed warheads and between 500 and 1,100 missiles, bombers and submarines. The United States is also seeking Russian support for tougher measures at the United Nations to pressure Iran to stop any development of a nuclear weapon and engage in talks on the scope and intent of its nuclear work. Clinton said it is hard to verify if Iran is closer to acquiring a nuclear weapons capability than when President Barack Obama took office last year. 'It's difficult to place timetables or milestones' on how far Iran may have come with clandestine activities, she said in the interview Friday. Asked if a lack of evidence that Iran is close to producing a weapon could undermine international support for sanctions aimed at reining in its nuclear program, Clinton said the sanctions push 'is making progress' and that she had a 'receptive audience' in her meetings with Russian leaders during the past two days. Russian Foreign Minister Sergei Lavrov said sanctions 'rarely work, but there are situations in which they become unavoidable.' Such a situation 'could emerge in Iran,' he told reporters Friday. Medvedev said this month that Russia is ready to consider sanctions that wouldn't hurt civilians. During her visit, Clinton urged her Russian hosts to delay plans to bring a nuclear power station into operation in Iran, saying 'we want to send an unequivocal message to the Iranians.' Russian Prime Minister Vladimir Putin said the Russian-built Bushehr plant's first reactor may begin work this summer. Clinton pointed to the United Nation's International Atomic Energy Agency's recent report that raised questions about Iran's nuclear program. 'Why were they building a secret facility at Qom?' she asked. 'Why would they not accept the joint Russian-French- American proposal' to assist them in getting nuclear fuel for a research reactor that produces medical isotopes. The U.S. is building support for 'a regime of smart sanctions, as President Medvedev has referred to them, that will try to change the behavior of the Iranian leadership,' Clinton told reporters after a meeting with the Russian leader. 'Increasingly, these questions are becoming important for the Chinese to also confront,' she said. China holds a U.N. Security Council permanent seat with veto power and hasn't yet said whether it would go along with more sanctions on Iran, a major supplier of crude oil for its economy. China is growing more concerned about Iran's nuclear intentions, Foreign Minister Yang Jiechi said this week. While the U.S. focuses on Iran's nuclear work, it is also trying to help democracy activists in Iran whose protests and online organizing have been targets of Iranian security crackdowns. Clinton said the U.S. has issued a license to a company to boost Internet access for Iranians, though the government in Tehran will likely attempt to block U.S. efforts. 'We're doing a lot, let me just put it at that, because we think it is in the interests of American values and American strategic concerns to make sure that people have a chance to know what is going on outside of Iran,' Clinton said. While in Moscow, Clinton joined a meeting of the Quartet on Middle East. The Quartet, made up of the U.S., United Nations, European Union and Russia, said indirect talks are 'an important step' toward resuming direct Israeli- Palestinian talks without preconditions. The Quartet said talks should lead to a settlement within two years and result in the emergence of a 'viable Palestinian state.' With assistance from Lyubov Pronina in Moscow. 