Islamabad, Pakistan ? Following four days of relatively tepid statements, former Prime Minister Benazir Bhutto on Wednesday issued a rousing call to action against President Pervez Musharraf’s declaration of emergency rule, setting up a possible direct confrontation between two titans of Pakistani power.

Bhutto, whose legions of rank-and-file supporters have been conspicuously absent from anti-Musharraf demonstrations this week, urged her backers to join in a major rally Friday in Rawalpindi, headquarters for the army, which Musharraf heads. After that, she said, opponents of emergency rule would begin “a long march” from the eastern city of Lahore to the capital, Islamabad. The 250-mile journey will take them through the heart of Pakistan’s largest and most politically influential province.

The government has officially banned protests, and the mayor of Rawalpindi said Bhutto’s demonstration would be suppressed. But Bhutto said she would go ahead with the rally. “I request my brothers and sisters to reach Rawalpindi at all costs,” she said at a news conference Wednesday afternoon. The Pakistani people, she said, are “under attack” and need to respond with action.

After she spoke, hundreds of boisterous Bhutto supporters attempted to march to the Parliament building but were beaten back by riot police wielding sticks and firing tear gas, a clash that might offer a small preview of what lies ahead.

Bhutto’s declaration could mark a significant escalation in the showdown between Musharraf and the country’s lawyers, human rights activists and political opponents who since Saturday have condemned the general for instituting de facto martial law.

Protests thus far have been lightly attended and quickly put down. But Bhutto has an unrivaled capacity to draw crowds in Pakistan, and just last month brought hundreds of thousands of cheering supporters to the streets of Karachi for her homecoming following eight years of exile.

Before her return, Bhutto and Musharraf had been in months-long power-sharing talks. Many Pakistani political analysts had speculated that even after the emergency declaration, she would not directly challenge Musharraf for fear of jeopardizing those negotiations.

But Wednesday, Bhutto gave Musharraf a 48-hour ultimatum to meet her demands or confront her in the streets.