Paris ? France accused Iran on Thursday of secretly making nuclear weapons, ditching Europe’s traditional diplomatic caution for bluntness in remarks that echoed the tough U.S. stance on Iran’s disputed nuclear program.

The accusation from French Foreign Minister Philippe Douste-Blazy – which Iran quickly denied – appeared to reflect mounting exasperation and a tougher stance by one of three key European negotiators.

“No civilian nuclear program can explain the Iranian nuclear program. It is a clandestine military nuclear program,” Douste-Blazy said on France-2 television.

By contrast, though, German Chancellor Angela Merkel said Thursday that she was “truly optimistic, I would even say very optimistic, that we can do everything to solve this conflict with diplomatic means.”

The board of the International Atomic Energy Agency voted last month to refer Iran to the U.N. Security Council, but Russia, a close ally of Iran, insisted that the council not take up the file until March. Last week, Iran resumed small-scale uranium enrichment, insisting the program is for nuclear energy, not arms, but still heightening tensions.

The next big test comes at Iranian-Russian talks starting Monday in Moscow on a Russian proposal to move Iran’s enrichment program to Russia and abandon enrichment on Iranian soil for a significant period of time.

The proposal is meant to allay fears that Tehran might misuse the technology to make nuclear arms.