"We will postpone talks with [the Iran Six] until the end of August due to their misconduct in imposing resolutions against Iran in the UN Security Council," Ahmadinejad told a news conference in Tehran, according to ISNA news agency.

"This is a penalty for them to be disciplined and learn the way of talks with the Iranian nation," he said.

Ahmadinejad said Iran will only resume talks with the Iran Six, made up of Russia, the United States, Britain, France, Germany and China, in the second half of the Muslim festival of Ramadan, falling this year to late August.

"We need to know what are the goals of those who want to hold talks with us?" he said. "Do they seek enmity or talks?"

Ahmadinejad said last Thursday he would disclose new conditions for talks to the Iran Six the following week, but has so far failed to do so.

Western powers suspect Iran of attempting to build nuclear weapons and the UN Security Council approved on June 9 the fourth round of economic sanctions against Iran over its nuclear program, including tougher financial controls and an expanded arms embargo.

Tehran maintains that its nuclear program is aimed at generating peaceful civilian energy.

The UN Security Council voted on June 9 in favor of a fourth round of sanctions against Iran for failing to halt its uranium enrichment program.

The UN sanctions include tougher financial controls and an expanded arms embargo, as well as an asset ban and a travel freeze on more than three dozen companies and individuals.