Diplomats at the United Nations nuclear agency say China and Russia are not prepared to join the United States and Europe in a statement urging that Iran suspend uranium enrichment.
The diplomats spoke as the board of the International Atomic Energy Agency met for a second day Tuesday, in Vienna.
But China and Russia have joined France, Germany, Britain and the United States in offering Iran an incentives package to suspend uranium enrichment and join talks on its nuclear program.
On Monday, U.S. ambassador to the IAEA, Gregory Schulte, said he hopes Iran will take advantage of what he calls an "enormous diplomatic opportunity."
Non-aligned nations at the Vienna meeting are expected to issue their own statement backing Iran's right to a nuclear program.
The incentives package agreed to by the United States, China, France, Russia, Britain and Germany is said to include international support for Iran's effort to build a nuclear power plant. The U.S. also would agree to drop some trade sanctions and allow Iran to buy spare parts for its aging fleet of American-made aircraft.
The proposal is believed to include a threat of sanctions if Iran fails to curb its nuclear activities.
The U.S. and Europe suspect Iran is trying to develop nuclear weapons - a charge Iran denies.