The radical Shi'ite cleric Moqtada al-Sadr has told a crowd of thousands of followers in Iraq to "say no to America".
He was making his first speech since returning to his stronghold in Najaf after more than three years of self-imposed exile in Iran, the BBC reports.
Last month his movement secured a deal to join the new government with seven ministries and 39 seats in Parliament.
Moqtada al-Sadr said Iraq is still occupied and its people are still resisting.
He led the crowd in chants against Israel and the United States.
The cleric told the enthusiastic crowd of followers to give the country's new government a chance. He exhorted Iraqis to forget what happened in the past stand shoulder to shoulder, helping the government to provide services.
His militia, the Mehdi Army, clashed several times with American and Iraqi forces after the 2003 US-led invasion.