Baghdad ? Iraq’s prime minister pledged Thursday to expand his crackdown on Shiite militias to Baghdad, despite a mixed performance so far against militants in the southern city of Basra.

The U.S. ambassador, meanwhile, said that despite a “boatload” of problems with the Basra operation, he was encouraged that the Shiite-led government was finally confronting extremists regardless of their religious affiliation.

Iraqi forces launched a major operation March 25 to rid Basra of Shiite militias and criminal gangs that had effectively ruled the city of 2 million people since 2005. But the offensive stalled in the face of fierce resistance from the militiamen and an uprising across the Shiite south spearheaded by the Mahdi Army of anti-American cleric Muqtada al-Sadr.

Fighting eased Sunday when al-Sadr ordered his fighters to stand down under a deal brokered in Iran.

Nevertheless, Prime Minister Nouri al-Maliki, himself a Shiite, insisted that the campaign to reclaim Basra was on track and that he would soon go after “criminal gangs” in Baghdad and elsewhere.

Al-Maliki specified two Baghdad neighborhoods – Sadr City and Shula – where the Mahdi militia holds sway and where U.S. and Iraqi forces have clashed with militants in recent days.