Iran’s response to an incentives package aimed at defusing a dispute over its nuclear programme is unacceptable, US officials said, making the prospects of new sanctions against the country more likely.

President Robert Mugabe’s regime struck at his rivals only two weeks before Zimbabwe’s presidential run-off, twice detaining his challenger and jailing the number two opposition leader to face treason charges.

Iranian President Mahmoud Ahmadinejad told world leaders his country will defy any further UN Security Council resolutions imposed by “arrogant powers” seeking to curb its nuclear programme.

The US is awaiting a formal UN deadline before seeking any new measures to coerce or punish Iran over its disputed nuclear programme, the State Department says.

The United States said today an offer by Iran to hold negotiations on its nuclear weapons but not to halt enriching uranium falls short of UN demands.