Holding posters of the late Iranian spiritual leader Ayatollah Khomeini and supreme leader Ayatollah Ali Khamenei, worshippers chant slogans during Friday prayers at the Tehran University campus in Tehran, Iran.

Tehran, Iran ? Iran’s supreme leader sought Friday to end the deepening crisis over disputed elections with one decisive speech — declaring the vote will almost certainly stand and sternly warning opposition leaders to end street protests or be held responsible for any “bloodshed and chaos” to come.

But a first sign of possible resistance came shortly after nightfall in Tehran. Cries of “Death to the dictator!” and “Allahu akbar” — “God is great” — rang from rooftops in what’s become a nightly ritual of opposition unity.

The sharp line drawn by Iran’s most powerful figure, Ayatollah Ali Khamenei, is a gambit that pushes Iran’s opposition to a pivotal moment: either back down or risk a crushing response from police and the forces at Khamenei’s disposal — the powerful Revolutionary Guard and their volunteer citizen militia, the Basij.

It also presents important tests for opposition leader Mir Hossein Mousavi.

He now must examine his willingness to challenge the Islamic leadership he once served as prime minister. There are further questions about his ability to control his own followers, who are waiting for a clear response to Khamenei’s edict before a rally planned for today.

Since the June 12 election, Mousavi has become the figurehead for a broad collection of demonstrators — from the most liberal-leaning reformists to religious conservatives — brought together by claims that fraud was behind the landslide re-election of President Mahmoud Ahmadinejad.

Some could be prepared to take their protests to the limit.

Many others, however, have no interest in an all-out mutiny against the country’s Islamic system and know authorities have the tools to strike back without mercy.

Khamenei was blunt about what a wider fight would bring — warning those who “want to ignore the law or break the law” will face the consequences.

“They will be held accountable for all the violence, bloodshed and rioting,” he told tens of thousands of people gathered for Friday prayers at Tehran University for a speech that was broadcast around Iran and the world.

Police clashed with protesters in running battles around Tehran immediately after the election and the Basij militia had a reported role in attacks at the university. Gunfire from a Basij compound in Tehran also left at least seven people dead Monday.

Khamenei even offered muted criticism of security forces, saying he objected to “misconducts” such as attacks on students.

But the full force of the police and Revolutionary Guard has remained in check. And this was Khamenei’s implicit message since the Guard and the vast volunteer militia force it controls is under direct command of the ruling clerics.