The US has intelligence agents in Iran but it is not clear if they are providing help to the protest movement there, a former US national security adviser has told Al Jazeera.

Brent Scowcroft said on Wednesday that "of course" the US had agents in Iran amid the ongoing pressure against the Iranian government by protesters opposed to the official result of its presidential election.

But he added that he had no idea whether US agents had provided help to the opposition movement in Iran, which claims that the authorities rigged the June 12 election in favour of Mahmoud Ahmadinejad, the incumbent president.

"They might do. Who knows?" Scowcroft told Josh Rushing for Al Jazeera's Fault Lines programme.

"But that's a far cry from helping protesters against the combined might of the Revolutionary Guard, the militias and so on - and the [Iranian] police, who are so far completely unified."