French prime minister Francois Fillon said world powers would have to take new action against Iran in the next few weeks if Tehran continues to reject Western proposals on its disputed nuclear programme.
Fillon said he was worried by a new report by the International Atomic Energy Agency (IAEA) this week which said Iran may be working to develop a nuclear-armed missile.
"We have read the new report (on Iran) by the IAEA ... and it is very worrying," Fillon told a news conference in Damascus alongside his Syrian counterpart Naji al-Otari.
"We proposed dialogue to Iran for several months and for the moment all the propositions have been turned down," he said.
"If the situation does not change, we have no other solution but to look into new measures in the coming weeks."
The United States is leading a push for a fourth round of United Nations Security Council sanctions against Iran because of suspicions it is secretly developing a nuclear arsenal.
Washington has been supported from fellow Security Council members Britain and France, while Russia, which has been more reluctant to impose more sanctions, has said it was now "very alarmed" by the IAEA report.
China has so far resisted imposing more sanctions.
Iran denies it is trying to develop a nuclear weapon and says the accusations of Western countries are baseless.
Syria, an ally of Iran, said Tehran was developing nuclear energy towards peaceful ends.
"Nothing justifies the fear over this issue," said al-Otari. "We think that it''s a right ... of all peoples to have nuclear energy for civil purposes," he said, but added that Israeli nuclear arms were a threat to world peace.
"We still hope that the international community ... will apply the same criteria to everyone," he said.
Fillon also asked Damascus for assistance in preventing Iran making decisions which were "dangerous to world peace".
"Peace in the region comes via a change in attitude of the Iranian government," Fillon said.
For several years, the IAEA has been investigating Western intelligence reports indicating Iran has coordinated efforts to process uranium, test explosives at high altitude and revamp a ballistic missile cone in a way suitable for a nuclear warhead.
