Troubled Sunday Coming in Iran?

According a report from PBS Tehran Bureau, the opposition leader from the last election and subsequent uprising, Mousavi, has called for demonstrations on Sunday.  What makes it even more of a concern is the conflict within the Revolutionary Guard:

12:00 p.m./Feb 18 As we described on the eve of the 25 Bahman demonstrations, there was a report that Major General Mohammad Ali Jafari, the Revolutionary Guard commander, had expressed his doubt that Guard enlisted men would be willing to use violence against marchers. The Telegraph reports that reluctance of that sort is now being voiced at much higher ranks:

Senior officers in Iran's Revolutionary Guards have written a letter to their commanding officer demanding assurances that they will not be required to open fire on anti-government demonstrators. 

Following the recent violence that occurred during anti-government protests in Egypt, the officers argue that it is against the principles of Shi'ite Islamic law to use violence against their own people.

In a suggestion of a major split within the Islamic Republic's ruling hierarchy over its handling of anti-government protests, the letter has been circulated widely throughout the ranks of the Revolutionary Guards, the body responsible for defending religious system.

The letter, a copy of which has been seen by the Daily Telegraph, is addressed to Major Gen Jafar [...] It calls on [him] to issue guidance to both the Revolutionary Guards and the Basij paramilitary militia to use restraint when handling anti-government protests.

While trouble flares across the Middle East and North Africa in the wake of events in Egypt, Yemen and Tunisia, the biggest questions remaining are (1) how Egypt turns out and (1A) what happens in Iran.