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Iran's elite security force is warning the opposition against holding any rallies this week as the nation marks 30 years since the seizure of the U.S. embassy in Tehran.
The Revolutionary Guards statement called on Iranians to watch out for "false slogans" and "plots by the enemy's agents" during anti-American, pro-government demonstrations planned for Wednesday.
For the past few weeks, opposition groups have called for renewed protests on that day to again raise the issue of the disputed June re-election of President Mahmoud Ahmadinejad.
Top opposition figures have appeared to back the call, with Mir Hussein Mousavi and Mohammad Khatami in recent days offering their support to demonstrators.
Such developments, after nearly five months and thousands of arrests in a post-election crackdown, continue to keep the government on alert.
The co-director of the London-based British-American Security Information Council, Paul Ingram, says the depth of opposition anger is not likely to go away soon.
"There is certainly a concern that if these rallies were allowed to happen then certainly they could spark a series of unrest over several weeks that could threaten the regime," he said.
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The annual celebrations are meant to recall the early, heady days of the Islamic revolution, when militants in the young republic overran the U.S. embassy, a symbol of the "Great Satan." But in the months since the June vote, several pro-government traditions have been turned on their heads.
Chants of "Death to America" have been replaced by some with "Death to Russia," for Moscow's quick recognition of Mr. Ahmadinejad's win. The annual pro-Islamic al-Quds Day in September saw mass anti-government demonstrations. And the nighttime calls from rooftops of "God is Great," that 30 years ago were in defiance of the Shah, are now directed at the regime that forced him from power.
Political analyst Paul Ingram says the use of revolutionary symbols is an important part of the internal dialogue.
"There are fluid relationships within Iran and a number of the more conservative and religious elements have been increasingly vocal in their public criticism of the government. And the opposition has chosen to attempt to use the Iranian Revolution, the memory of it, in opposition to the current government," he said.
But opposition leader and former president Khatami hinted that revolutionary ideals may go only so far in the face of the government crackdown. He told supporters Saturday that "if we who believe in the basis of the system cannot speak, others who do not believe in it will take action."