– Warming U.S.-Iranian relations do not mean that the United States will back off its demands about Iran's nuclear program, or roll back missile defenses in Europe aimed at intercepting an Iranian attack, Secretary of State John Kerry said Monday.

Iran's foreign minister, who met with Kerry last month at the United Nations, was quoted in state media Sunday as saying the United States should bring new proposals to a nuclear bargaining session next week. Kerry appeared to reject that, saying Iran still hasn't responded to the last offer put forth by the United States, Russia and others in February.

"We're waiting for the fullness of the Iranian difference in their approach now," Kerry said, following a meeting here with Russian Foreign Minister Sergei Lavrov. "But we're encouraged by the statements that were made in New York, and we're encouraged by the outreach."

Iranian President Hassan Rowhani argued at the U.N. General Assembly last month that Iran's program is not dangerous and that his country will cooperate with monitors to prove that. Sanctions are counterproductive and should end, he argued.

On the sidelines of the U.N. meeting in New York, Kerry had an unusual meeting with Iranian Foreign Minister Mohammad Javad Zarif, and President Obama phoned Rowhani for the first direct contact between leaders of the two nations since before the 1979 Iranian revolution and takeover of the U.S. Embassy.

Lavrov, who plans to attend next week's much-anticipated nuclear meeting in Switzerland, said the international group negotiating with Iran wants "a road map which would, at the end of the day, satisfy the international community that the Iranian nuclear program is entirely peaceful" and put under the full control of international nuclear monitors.

"Iran probably wants more clarity, more specific steps to be spelled out on the road to the result which we all want to achieve," Lavrov said. "And I think this would be discussed next week in Geneva."

A Russian reporter asked Kerry whether the apparent thaw in the long U.S.-Iranian enmity means that the missile defense architecture that is being built by the United States to protect Europe is no longer needed. Russia has been opposed for years to U.S. plans to defend European allies with a network of interceptors. The United States insists that the system is defensive and is being constructed with Iran in mind, but Russian leaders have long questioned that assertion.

While Washington is eager to explore the possibility of a negotiated settlement with Iran over its disputed nuclear program, it's too early to say whether the thaw begun at the United Nations last month will lead to a change in U.S. policy, Kerry said.