Iran’s clerical dictatorship cracked down on opposition protests today and is sure to mount an even more forceful response to the reported bombing of the mausoleum of the founder of Iran’s Islamist revolution, Ayatollah Khomeini. A suicide bomber apparently blew himself up inside the shrine, wounding two people. It is unclear from initial reports if a group is responsible or if the man acted alone. But the regime is likely to exploit the bombing, which will enrage Khomeini’s many admirers in Iran, and use it as a pretext for a reign of terror.

Tehran police today clamped down on opposition rallies, using water cannons and tear gas to disperse crowds that had gathered in defiance of Ayatollah Khamenei’s order to stop their popular protests against the regime. Police occupied the sites of several planned rallies, including Revolutionary Square, and prevented crowds from gathering. Despite their efforts, demonstrators held smaller impromptu rallies and tension is building. Both sides are digging in for a confrontation that could soon erupt in extended violence.

Khamenei gave a rare televised speech at Friday prayers at Tehran University in which he denied that the elections had been rigged, again proclaimed President Mahmoud Ahmadinejad the winner, and called for a halt in the huge popular demonstrations against the election results, which increasingly have morphed into protests against the ruling regime. Khamenei defended President Ahmadinejad, who was sitting in the front row at the televised speech, saying that political opponents had unfairly called him a liar. But the ayatollah also criticized Ahmadinejad for charging that some high-ranking clerics, including former president Rafsanjani, were corrupt. Ominously, he warned that if the protests erupted in bloodshed, the opposition politicians who called for them would be blamed.

Many Iranians remain committed to continuing the demonstrations despite the ayatollah’s firm warning, however. Friday night, protesters again defied the regime by climbing to their roofs to chant “Death to the Dictator” and “God is Great.”

It appears that this test of wills could soon erupt in more extreme violence when the Basij, the paramilitary thugs who do the regime’s dirty work, are unleashed to intimidate the opposition.

While the Obama Administration continues to mute its criticism of the clerical regime in hopes of salvaging its floundering diplomatic engagement strategy, both the Senate and the House of Representatives pointedly disagreed yesterday and passed resolutions that denounced the regime’s repression of the Iranian people by overwhelming votes. Rep. Mike Pence, who co-sponsored the resolution in the House, said “When Ronald Reagan went before the Brandenburg Gate, he did not say Mr. (Mikhail) Gorbachev, that wall is none of our business,” referring to President Reagan’s famous exhortation to the Soviet leader to “tear down that wall.”