Ahmed al-Shaibani, a senior Sadr aide, warned US forces not to take advantage of the order, while another said the suspension might last only a week if US and Iraqi forces did not stop detaining the cleric's followers.
   
"We say to the Americans, don't be happy. The resistance does not end," Shaibani said.

'Wait and see'

The Pentagon cautiously welcomed the six-month truce.
  
"The proof of Muqtada al-Sadr's sincerity is in the pudding,"  Brigadier General Richard Sherlock, deputy director for operational planning at the US department of defence, said.
  
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Who is Muqtada al-Sadr?

"We have to wait and see. We need to see actions that correspond to that as opposed to just calls for calm."

The US military has welcomed an order given by Muqtada al-Sadr, the Iraqi Shia leader, to freeze his militia's activities following deadly clashes in southern Iraq.
 
Lieutenant Colonel Chris Garver, the US military spokesman in Iraq said: "Any time someone in Iraq, especially a leader, wants to use non-violent methods to solve problems ... we encourage this."
 
An aide said al-Sadr had suspended armed action by his 60,000 member militia to remove rogue elements.

Hazim al-Araji, an aide to al-Sadr, read a statement from the Shia leader saying "we declare the freezing of Mahdi Army without exception in order to rehabilitate it in a way that will safeguard its ideological image within a maximum period of six months starting from the day this statement is issued."
 
Asked if Wednesday's unexpected order meant no attacks on US troops, another senior aide who declined to be identified said: "All kinds of armed actions are to be frozen, without exception."

Corrupt leaders

Abu Ali, another Mahdi Army commander in Sadr City, said the suspension order would expose corrupt leaders.
   
"There are some bad leaders in the Mahdi army who should have been replaced a long time ago"

Abu Ali,
Mahdi Army commander
"There are some bad leaders in the Mahdi Army who should have been replaced a long time ago ... Through this order the corrupt elements will show their faces, because they will not comply," he said.

US forces have previously said that many attacks against them and Iraqi security forces are the work of "rogue" Mahdi Army groups, who may not operate under al-Sadr's full control.
 
The decision had been taken after 52 people were killed in the southern Iraqi city of Karbala in fighting between the Mahdi Army and another Shia bloc - the Supreme Iraqi Islamic Council (SIIC), whose armed wing controls much of the south.
 
On Thursday, Iraqi security forces arrested 72 fighters following the Karbala clashes, the defence ministry said.
 
A ministry statement said a number of weapons had also been confiscated during a search of homes across the southern city.
 
Test of authority

Analysts said al-Sadr's six-month order would be a test of his authority over the group, which is believed to have fragmented and, according to the US, has received funding, training and weapons from Iran.
 
Also on Wednesday, Nuri al-Maliki, the Iraqi prime minister, said that fighters from the Mahdi Army and the SIIC who were involved in the violence in Karbala had wanted to blow up the Imam Hussein shrine, one of the holiest to Shia Muslims.
 
"From our initial investigation, we found some evidence of who did this act ... the intention of this act was to storm into the shrine of Imam Hussein and blow it up," al-Maliki said from inside the shrine during a visit to Kerbala, 110km south of Baghdad.
 
The Mahdi Army denied the allegation.
 
While his ministers have left the cabinet, al-Sadr's political bloc holds 30 seats in parliament and is still part of the ruling Shia alliance.