But Iranian officials now sound more conciliatory. Even President Mahmoud Ahmadinejad has been uncharacteristically quiet after earlier insisting Iran would not give in to "bullying powers" over nuclear plans Tehran says are peaceful.

Some Western diplomats detect a more positive approach from Iran and say any knee-jerk public statements have turned to more careful reflection. "There is a debate," said one.

However the diplomat said it was not clear Iran would accept suspension or even a "freeze-for-freeze" idea to get preparatory discussions going, a step involving Iran freezing expansion of nuclear work in return for world powers halting moves to add to three rounds of U.N. sanctions already imposed.