Moscow ? Russia publicly pushed back Tuesday against U.S. efforts to threaten tough new sanctions if Iran fails to prove its nuclear program is peaceful, dealing an apparent setback to President Barack Obama’s hopes for Moscow’s backing for fresh penalties against Tehran.

Russian Foreign Minister Sergey Lavrov said Moscow believed such threats were “counterproductive” and that only negotiations should be pursued now. Just last month, Russian President Dmitry Medvedev had said that sanctions are rarely productive but “in some cases they are inevitable,” a statement the U.S. hailed as a shift of opinion in Moscow.

Lavrov, at a joint news conference Tuesday with Secretary of State Hillary Rodham Clinton, said diplomacy “still has chances to succeed.”

“At the current stage, all forces should be thrown at supporting the negotiating process,” Lavrov said. “Threats, sanctions and threats of pressure in the current situation, we are convinced, would be counterproductive.”