US ally Turkey said on Saturday Washington's efforts to isolate Iran over its nuclear programme were undermining reformists in Tehran and bolstering Iranian influence across the Middle East.
Foreign minister Ali Babacan said the US was failing to win broad support for tougher sanctions against Iran, and called instead for dialogue and diplomacy.
"Simply isolating Iran in our view caused Iran to be more united, to weaken the hands of the reformists," Babacan told reporters on the sidelines of the World Economic Forum (WEF) in Davos.
"Also [it led to an] Iran which had more and more influence in the region. That is the reality we are observing."
The US and other Western powers say Iran's refusal to stop enriching uranium supports their suspicion that Tehran is seeking nuclear weapons. Iran says its nuclear programme is peaceful and has ignored repeated UN demands that it cease enrichment.
Foreign ministers of the US, Britain, France, Germany, Russia and China agreed on an outline proposal for new sanctions against Iran this week
Western powers had to soften some proposed measures to meet Chinese and Russian demands. But EU and US diplomats said they were the latest step in a gradual expansion of sanctions against Iran and would almost certainly be followed by further penalties if Tehran remained defiant.
Babacan said Washington was struggling to get broad support for its stance.
"Bringing all the international community together with stronger sanctions is not happening," he said.
"They are finding it difficult to implement that. Just to have stricter and stricter sanctions ironically gives more power to Iran."
