The US has been funding bomb attacks and the seizure of hostages inside Iran.
The US television station ABC revealed that the US has been channelling funds to an armed group operating out of Pakistan.
US officials in Washington have previously linked the group to the Taliban in Afghanistan.
More than a dozen Iranian soldiers and officials have been killed or kidnapped by the group, called Jundullah (Soldiers of God), which operates out of the Baluchistan province in Pakistan, just across the border from Iran.
Jundullah claimed reponsibility for a bus bombing in the Iranian city of Zahedan two months ago which killed 11 Revolutionary Guards.
Sources inside the Pakistani government say the secret campaign against Iran by Jundullah was one of the issues on the agenda for discussion when US vice-president Dick Cheney met with Pakistani president Pervez Musharraf in February.
ABC has continued to stand by its story despite vigorous denials by officials from the CIA and the Pakistani foreign office.
The US government-funded Voice of America’s Persian news service interviewed Jundullah’s leader, Abdul Malek Rigi, last month. They introduced him as the “leader of the Iranian people’s resistance movement”.
Aside from the major US naval build up in the Persian Gulf, which already involves two aircraft carriers and several cruise missile equipped warships, the US is building a military base in Azerbaijan, on Iran’s northern border.
The US media has also reported that American intelligence teams have been operating with Kurdish groups, carrying out attacks from northern Iraq across the border into Iran.
Meanwhile an Iranian diplomat who was abducted in Baghdad and held for two months claims he was tortured by his CIA captors.
The diplomat, Jalaf Sharafi, says he was seized by members of the Iraqi military who were driving US coalition vehicles.
He was held at a base near Baghdad airport where he was questioned in Arabic and English about Iran’s influence in Iraq.
He was then released by being dumped from a vehicle at the back of the airport complex.