"I think that cooperation between Russia and the United States has been very beneficial in getting Chinese participation" towards a UN resolution on Iran, Clinton said in response to a question from a student following a speech at the University of Louisville in Kentucky.
Countries such as Iran and North Korea, she added, are "finding it more and more difficult to make the case that they don't have their own responsibilities."
President Barack Obama signed the landmark deal Thursday in Prague with his Russian counterpart Dmitry Medvedev, under which the two countries will slash their stockpiles of nuclear weapons by roughly 30 percent against a previous treaty from 2002.
"Can our efforts to bring the new START Treaty into force help persuade other nations to support serious sanctions against Iran? I believe they could," said Clinton after noting the move to reduce stockpiles was not likely by itself to convince Iran or North Korea to change their behavior.
But Beijing has "become convinced over the last month" of the need for action on Tehran's suspect nuclear program, she added.
China's ambassador to the United Nations on Thursday joined envoys from Britain, France, Russia, the United States and Germany to mull a US draft resolution that would slap sanctions on Iran's powerful Revolutionary Guards, believe to be involved in nuclear proliferation activities.
Beijing confirmed it would meet again with the world powers in New York to discuss the next steps against Iran, although foreign ministry spokeswoman Jiang Yu insisted Beijing "still believes dialogue and consultation are the best way to solve the nuclear issue."
China has until now refused to back Western calls for new sanctions against Tehran, and last week played host to the Islamic republic's chief nuclear negotiator.
Beijing has a close diplomatic and trade relationship with Iran, dominated by its imports of Iranian energy resources.
