Iran should stop backing extremist groups that contribute to ongoing violence in Iraq, adding that the US is watching Teheran "very, very closely," Gen. David Petraeus said on Saturday. The American commander of the region that includes both countries also told a US-Islamic world forum in Qatar on Saturday that the US is looking for signs that Iran is willing to cooperate, echoing gestures of openness expressed by the Obama administration. However, he was firm when asked what concrete steps Iran could take to improve relations. Petraeus says there could be an end to the "training, equipping, funding of extremist elements" in the region. He says Teheran's help to such group continues to contribute to violence in Iraq.