Rice warned Tehran on Thursday that it was not immune to the "major changes" in the region.


"The Iranians should not consider themselves immune from the major changes that are going on in the region, and we would hope that they would begin to engage in more stabilising behaviour," Rice said.


Rice, who reiterated US concerns over Tehran's nuclear programme, described Iran as a "state sponsor of terrorism" that is "out of step with a region that is trying very hard now to move toward a two-state solution", a reference to Israel and the Palestinians.


Iran urged to help Iraq 


Another senior US official, Undersecretary of State for Political Affairs Nicholas Burns, separately told the Senate Foreign Affairs Committee that Washington would like Iran to help Iraq boost its stability.


"What we would hope is the following: that Iran would play a much more positive and productive role in trying to support Iraq, as we are trying to support Iraq.


"But our suspicion has been that Iran did not play a constructive role in the many weeks and debates about the formation of the current Iraqi government," Burns said.


"And the key to a successful future for a united Iraq is to see this power-sharing agreement among the Shia, and Sunni, and Kurdish elements, and the Iranians don't seem to have spent much time supporting that goal of multi-ethnicity, of shared power," he said.