"We are rejoining the political process," Saleh Hassan Issa al-Igaili, a lawmaker from the cleric's parliamentary bloc, told AFP.

The move came amid a stepped-up US and Iraqi military offensive on Shiite militias, including Sadr's Mahdi Army, which is accused of stoking sectarian violence in Iraq.

The group, which has six ministers and 32 MPs in the 275-member Iraqi parliament, suspended its participation in the national assembly on November 29 in protest over Maliki's meeting with US President George W. Bush.

Known for its strong anti-US stance, the group announced its return to parliament two days after a senior Sadr aide was arrested by US and Iraqi troops in a raid on a Shiite religious site in Baghdad.

The arrest of Abdul Hadi al-Darraji sent a message to the militia loyal to Sadr -- the Mahdi Army -- which is accused by the US authorities of killing hundreds of Sunni Arabs in Baghdad's sectarian conflict.

Darraji, a spokesman for the movement in Baghdad, was arrested along with four others near the impoverished Shiite stronghold of Sadr City in the east of the capital.

The US military did not identify him by name but said it had arrested an illegal armed group leader involved in the torture and kidnapping of Iraqi civilians.

Kurdish lawmaker Mahmud Othman told AFP that the Sadr group's return was a boost for Maliki.

"It helps strengthen Maliki's position because they are allies," Othman said.

"It is also an indication by the Sadr group that they want to be part of the political process and not resort to violent methods at a time when Iraqi and US forces are targeting militias."

Igaili said the group ended the boycott after receiving a pledge from the parliament to establish a timetable for the withdrawal of US troops.

"We have also asked for a timetable for training Iraqi forces, and that the mandate for occupation troops not be renewed without consulting the parliament," Igaili added.

US forces are deployed in Iraq at the invitation of the national government and any parliamentary decision to expel them could trigger a political crisis.

The UN Security Council has renewed the US-led coalition's mandate until the end of 2007 at the request of Maliki's government.

During the first few days of its boycott, Sadr's group had announced plans to build an anti-US parliamentary alliance to demand the withdrawal of American troops from Iraq.

Sadr supporters claimed they had identified 100 members of parliament who wanted to send home the roughly 140,000-strong US force backing Maliki, but the issue was never put to a vote.

Parliament speaker Mahmud al-Mashhadani confirmed the return of Sadr's bloc following several weeks of talks.

"All recommendations of the committee formed for the return of the Sadr bloc to the parliament have been accepted," Mashhadani told a news conference.

Another Sadr MP, Baha Al-Araji said the group would attend the assembly session on Sunday.

Sadr had pulled his supporters out of the Shiite-led government in protest over Maliki's decision to meet Bush in Jordan for crisis talks in November.

A few weeks after their meeting, Bush announced plans to dispatch 21,500 more US troops to Iraq to quell sectarian violence.