The US secretary of state has urged Iran to resume talks with the European Union on its nuclear programme.
Ms Rice has won French support for US pressure on Iran
Condoleezza Rice was speaking after talks with French leaders, who along with Britain and Germany have tried to engage Iran in dialogue.
The US has accused Iran of secretly trying to develop nuclear weapons - a charge Tehran vehemently denies.
The US is threatening to refer Iran to the UN Security Council if it fails to scrap plans to enrich uranium.
"There is always the course of negotiation ... but there is also the course of the Security Council," Ms Rice said.
"It is therefore important that Iran negotiate in good faith."
France has previously argued in favour of a diplomatic approach, but on Friday Foreign Minister Philippe Douste-Blazy said referring the matter to the UN was a real option.
France, Britain and Germany had been negotiating with Iran over its nuclear programme but talks broke down in August, and Tehran has threatened to resume uranium enrichment.
Last month, the UN nuclear watchdog, the International Atomic Energy Authority (IAEA), supported a resolution threatening Iran with referral to the UN Security Council.
The IAEA will meet again next month, but it is still not clear if there is enough backing to refer Iran to the UN Security Council.
This week, Tehran said it would welcome the resumption of talks with the Europeans without preconditions.
When Ms Rice was last in Paris eight months ago, she spoke of opening up a new chapter in Franco-American relations, to heal the rift over the US-led war in Iraq.
Both sides insist they have put all major disagreements behind them and stress they are working together on a range of issues, including foreign policy.
Ms Rice has now arrived in Moscow for talks with Russian President Vladimir Putin.
Russia, which helped Tehran develop its nuclear facilities, abstained from voting on the IAEA resolution threatening Iran with referral to the Security Council.
After talks in Moscow, Ms Rice will travel to London for talks with UK Prime Minister Tony Blair and Foreign Minister Jack Straw.