"Today, France is waiting for a strong gesture from the Iranian authorities that would help restore confidence about the goal of its nuclear program," said foreign ministry spokesman Herve Ladsous.
Signing the NPT protocol, which would allow International Atomic Energy Agency (IAEA) inspectors to visit Iranian installations without prior notice, would constitute a "significant first step towards responding to our concerns," he added.
Ladsous's comments came after US President George W. Bush called on Europe to put more pressure on Tehran, which has repeatedly denied accusations that it is covertly developing weapons under the guise of a civilian nuclear program.
Earlier this month, European Union foreign ministers expressed their "increasing concern" over Iran's nuclear program and demanded Tehran's "unconditional" acceptance of the NPT protocol.
The European Union, which is negotiating a key trade pact with Iran, said it would review its cooperation with Tehran after the release of an IAEA report due in September about Iran's nuclear program.
In Washington on Wednesday, Bush said: "We've got to work in a collective way with other nations to remind Iran that, you know, they shouldn't develop a nuclear weapon.
"It's going to require more than one voice saying that, however. It's going to require a collective effort of the Europeans, for example, to recognize the true threat of an armed Iran to achieving peace in the Middle East."