BAGHDAD, March 27 (UPI) -- Supporters of Shiite cleric Moqtada Sadr took to the streets Thursday calling for the Iraqi prime minister to step down as violence continued in Basra.

A spokesman for Sadr, Salman al-Foureji, said the protesters accused Prime Minister Nouri al-Maliki of collaborating "with the occupation forces," Voices of Iraq said.

Meanwhile, U.S. military officials said the conflict between Shiite militias, including the Mahdi forces, and Iraqi security forces could escalate in the coming weeks but stressed the U.S. military would act only in a supporting role, The Washington Times said Thursday.

Sadr's backers accuse the U.S. military and Iraqi government of taking advantage of the extended cease-fire to liquidate its members.

Sadr called for an extension of a six-month cease-fire on March 1, promising those that violated the agreement would be disowned by the Sadrists. Sadr said, however, that forces could respond to attacks by U.S. and Iraqi forces.