Russian Foreign Minister Sergei Lavrov says his country "regrets" Iran's apparent rejection of the U.N.-backed proposal to send its uranium abroad to be enriched.
The remarks come amid signals both from the U.S., eager to take a tough stance on pressuring Iran, and China, which is reluctant to impose more sanctions.
Speaking at a press conference Friday, Lavrov said the U.N. Security Council could discuss sanctions, but he did not commit to supporting them.
Thursday, U.S. Secretary of State Hillary Clinton said the international community intends to put more pressure on Tehran.
She said, "We will not back down." She made the remarks in Washington between meetings with the new European Union chief diplomat, Catherine Ashton of Britain, and British Foreign Secretary David Miliband.
Clinton said she believes a path is open to a new U.N. Security Council resolution on Iran. Tehran denies its uranium enrichment program is part of an effort to develop nuclear weapons.
Clinton declined to predict whether the resolution would include new sanctions but stressed the entire world has reason to be concerned about a nuclear armed Iran.
Top diplomats from Britain, France, Germany, Russia, and the United States, and a lower level diplomat from China, met in New York Saturday to discuss the possibility of placing more sanctions on Iran.
A spokesman said the six countries will continue to seek a negotiated solution, but that they are also considering "appropriate further measures."
Clinton called the meeting a productive step toward unified international action.
In other news, the head of Iran's atomic energy agency said his country will begin operating its first nuclear power plant, built by Russia, by late September.
Russia agreed in 1995 to take over building the plant at Bushehr on the Persian Gulf but has repeatedly delayed its completion.
Moscow says the plant cannot be used for military purposes because it will come under supervision of the International Atomic Energy Agency, which means Iran will have to return all used fuel rods at the plant to Russia.
Some information for this report was provided by AFP and Reuters.