In a move that reflects Washington's growing concern with the failure of diplomatic initiatives, CIA officials are understood to be helping opposition militias among the numerous ethnic minority groups clustered in Iran's border regions.
The operations are controversial because they involve dealing with movements that resort to terrorist methods in pursuit of their grievances against the Iranian regime.
In the past year there has been a wave of unrest in ethnic minority border areas of Iran, with bombing and assassination campaigns against soldiers and government officials.
Such incidents have been carried out by the Kurds in the west, the Azeris in the north-west, the Ahwazi Arabs in the south-west, and the Baluchis in the south-east. Non-Persians make up nearly 40 per cent of Iran's 69 million population, with around 16 million Azeris, seven million Kurds, five million Ahwazis and one million Baluchis. Most Baluchis live over the border in Pakistan.
Funding for their separatist causes comes directly from the CIA's classified budget but is now "no great secret", according to one former high-ranking CIA official in Washington who spoke anonymously to The Sunday Telegraph.
His claims were backed by Fred Burton, a former US state department counter-terrorism agent, who said: "The latest attacks inside Iran fall in line with US efforts to supply and train Iran's ethnic minorities to destabilise the Iranian regime."