Thousands of people protest today in Basra, Iraq. The protesters, upset about poor city services, marched peacefully through the streets of Iraq's second largest city, demanding the provincial governor's resignation.

BAGHDAD — The radical cleric Muqtada al-Sadr ordered his followers in the Cabinet to abandon their posts today, the head of the cleric's parliamentary bloc said, blaming the Iraqi leadership's refusal to respond to demands for a timetable for a U.S. withdrawal.

The order, while unlikely to topple Prime Minister Nouri al-Maliki's regime, deals a significant blow to the U.S.-backed leader, who relied on support from the Sadrists to gain office.

Al-Sadr's ministers will "withdraw immediately from the Iraqi government and give the six Cabinet seats to the government, with the hope that they will be given to independents who represent the will of the people," said Nassar al-Rubaie, head of al-Sadr's bloc, reading a statement from the cleric.

Al-Sadr, who has tremendous influence among Iraq's majority Shiites, has been upset about recent arrests of his Mahdi Army fighters in the U.S.-led Baghdad security crackdown. He and his followers have also criticized al-Maliki for failing to back calls for a timetable for U.S. troops to leave the country.

At least 13 Iraqi soldiers were killed today when gunmen ambushed their military checkpoint near the northern city of Mosul, police said. Another four soldiers were wounded in the brazen attack, said police Brig. Saeed Ahmed al-Jibouri, director of Ninevah police.

Meanwhile, thousands upset about inadequate city services marched peacefully through the streets of Iraq's second largest city today, demanding the provincial governor's resignation.

Some 3,000 demonstrators gathered near the Basra mosque, then marched a few hundred yards to Gov. Mohammed al-Waili's office, which was surrounded by Iraqi soldiers and police officers. The protest ended a few hours later.