Washington: The top US commander in Iraq has accused Iran of being a significant destabilising force in Iraq, and of secretly providing support to Shia extremists.
General George Casey accused Tehran of training and arming insurgent groups and said "surrogates" regularly attacked US troops.
He said that although the US has no evidence of Iranians operating directly in Iraq, he assumed elements in Tehran were guiding the process, saying Iran's influence had risen recently.
Speaking at a Pentagon news conference with Defence Secretary Donald Rumsfeld, Casey said Iran's actions were "decidedly unhelpful," adding that intelligence on Iranian activities confirmed their suspicions.
The US has frequently accused Iran of helping Shia groups, but has offered little evidence of the alleged activities.
Casey said, "Since January we have seen an upsurge in their support, particularly to the Shia extremist groups. They are using surrogates to conduct terrorist operations both against us and against the Iraqi people."
He added, "We are quite confident that the Iranians, through the special operations forces, are providing weapons, IED (improvised explosive device) technology and training to Shia extremist groups in Iraq."
He suggested that Lebanon's Iranian-backed Hezbollah guerrillas were also likely to be involved in training Iraqi militias.