Iran's Supreme Leader Ayatollah Ali Khamenei says he does not believe that the opposition leaders responsible for post-election agitation in June were knowing agents of any foreign power.
Opposition leaders say dozens of people were killed and hundreds arrested during the protests after President Mahmoud Ahmedinajad was declared the winner of the election on 12 June with 63% of the vote.
Several government figures accused western countries of plotting to destabilise the Iranian revolution.
Correspondents say the ayatollah appears to be trying to reduce tensions.
In a statement read on Iranian television, Ayatollah Khamenei said:
"I do not accuse the leaders of the recent incidents to be subordinate to the foreigners, like the United States and Britain, since this issue has not been proven for me."
But he said there was "no doubt" the mass demonstrations, in which at least 30 people died, had been planned in advance, "whether its leaders know or not".
"This plot was defeated, since fortunately our enemies still do not understand the issue in Iran," he said.
"Our enemies were given a slap in face by the Iranian nation, but they are still hopeful and they are pursuing the issue."