The commander of Iran's powerful Revolutionary Guard accused former President Mohammad Khatami and other top reformists of challenging the authority of nation's supreme leader — a claim Wednesday that could signal Iran's crackdown on opposition figures may seek to reach higher.

The sharp attack by Gen. Mohammad Ali Jafari effectively labels Khatami and others as potential foes of the ruling system and could place them at higher risk of being directly punished by hard-line authorities.

Khatami's former vice president, Mohammad Abtahi, is among more than 100 activists and pro-reform politicians facing trial on charges of plotting against the Islamic regime following the disputed presidential elections in June.

But Khatami and several other opposition leaders — including the election challengers to President Mahmoud Ahmadinejad — have not been detained.

Jafari's accusations could open more room for action against Khatami and others such as Mir Hossein Mousavi, whose backers say was robbed of victory by massive vote fraud. It also pointed to possible new rifts in the establishment about how to deal with the top opposition figures.

Jafari was quoted by the official Islamic Republic News Agency as claiming Khatami and allies encouraged the massive street protests after the vote and tried to undermine the authority of Supreme Leader Ayatollah Ali Khamenei, who holds the pinnacle of power in Iran's theocracy.

Last week, Khamenei appeared to offer some greater protection for the opposition leaders, saying he had seen no evidence to back up claims they had links to foreign powers. But the Revolutionary Guard — which has shown increasingly loyalty to Ahmadinejad — seems determined to increase pressure on Khatami and others after Iran's worst internal turmoil since the 1979 Islamic Revolution.

"The goal of postelection riots was to bring a change in the behavior of the Islamic Republic, a change in directions, a deviation from principles," Jafari was quoted as saying.

He also directly accused Khatami of making statements earlier this year indicating reformists want to erode the supreme leader's powers, but offered nothing further to back up the claim.

Jafari went on to repeat charges that opposition leaders had plotted a "velvet revolution" — citing confessions from some defendants in the mass trial of pro-reform backers.

Opposition groups have denounced the trial as a "ridiculous show" and said the self-incriminating statements from detainees were obtained while facing intense pressures and possible abuse in custody.

Khatami was not immediately available for comment Wednesday.

His two terms in office, from 1997 to 2005, were marked by an opening of greater personal and political freedoms in Iran. But it also was tangled in unending confrontations between groups pressing for more liberal changes and conservatives fighting to keep their influence from slipping further.

One of the most sensitive battles was the powers of the supreme leader, who has the final say on all state matters and is considered by hard-liners to stand above the law and answerable only to God.

Some of Khatami's backers had urged for greater counterweights to the leader's vast authority. Those daring to directly challenge Khamenei, however, have either been jailed or forced out of politics.

Jafari called the postelection protests "the biggest challenge" to the ruling system and claimed it was planned in advance.

But reformists say Ahmadinejad's re-election was an internal plot by hard-liners to rig results. The Revolutionary Guard also has come under accusations of abuses during the backlash to crush street demonstrations and round up suspected opposition figures.

Even some conservatives have turned against Ahmadinejad, saying the crackdowns have gone too far and complaining he is trying to steamroll any competing political voices.

A key test for Ahmadinejad could come Thursday when parliament is expected to vote on his choices for the 21-seat Cabinet. Already, lawmakers have questioned whether some nominees have enough experience and expertise for the posts.