In ordering his militia to stop fighting, al-Sadr also demanded concessions from the Iraqi government, including an end to the "illegal raids and arrests" of his followers and the release of all detainees who have not been convicted of any offenses.
Sadrists in Basra complained police were still conducting raids in the area Monday night and that their followers might start carrying weapons again for self-defense.
Government spokesman Ali al-Dabbagh welcomed al-Sadr's decision but told reporters Monday that no political group was above the law. Al-Sadr's supporters believed the security crackdown in Basra was aimed at weakening their movement before provincial elections this fall.
US and Iraqi officials insisted the operation was directed at criminals and rogue militiamen -- some allegedly linked to Iran -- but not against the Sadrist movement, which controls 30 of the 275 seats in the national parliament.
But well-informed Iraqi political officials said the Iranians played a key role in hammering out the peace deal, boosting the Islamic Republic's influence among the majority Shiite community. The officials spoke on condition of anonymity because of the sensitivity of the information.
According to one Shiite official, the deal was struck after hours of negotiations in the Iranian holy city of Qom involving key figures in Iraq's major Shiite parties and representatives of the Iranian Revolutionary Guard.
Two of the Iraqis present -- Ali Adeeb and Hadi al-Amri -- presented documents and photos which they claimed proved that al-Sadr's militia was receiving Iranian weapons, the official said.
Shiite-dominated Iran is believed to supply weapons, money and training to most Iraqi Shiite factions -- a charge the Iranians deny.
The Iraqi officials would not elaborate on Iran's role, and efforts to contact Iraqi representatives who took part in the Qom meetings were unsuccessful.
Iran has been eager to maintain unity among Iraq's factious Shiites, believing that is the best way to ensure a pro-Iranian government in Baghdad.
"By all reports, Iran's role is not good," said Michael O'Hanlon, foreign policy expert at the Brookings Institution. "They're arming all groups. ...They want influence with everyone."
A day after al-Sadr's call, Iraqi officials sought to present his decision as a victory for the government, despite the failure of US-backed Iraqi forces to dislodge Mahdi fighters from Basra strongholds.
Al-Dabbagh said security operations in Basra would continue until the city "reaches a secure and acceptable situation" where residents can live "without threats or terrorism from any side."
Maj. Gen. Abdul-Karim Khalaf said that as of Monday, Iraqi forces had killed 210 "criminals" in Basra, arrested 155 others and seized large quantities of rockets and roadside bombs.
Nonetheless, the outcome of the Basra crisis dealt a blow to the credibility of al-Maliki, who flew to the city last week to oversee the crackdown personally.
On Saturday, al-Maliki had promised "a decisive and final battle" and gave assurances he would remain in Basra until the militias were crushed. A key adviser to al-Maliki, Sami al-Askari, said the prime minister was expected to return to Baghdad this week.
With tensions easing, Iraqi government television reported that a high-profile official was released Monday evening four days after he was seized by gunmen from his east Baghdad home.
Tahseen al-Shiekhly serves as the civilian spokesman for the Baghdad military command and regularly appears before reporters to tout improvements in security.
In Basra, residents said by telephone that the city, headquarters of Iraq's vital oil industry, was generally calm except for sporadic explosions and machine gun fire.
Some residents, however, estimated that only about a quarter of the shops and businesses opened Monday because any people were apprehensive that the truce would hold.
"The whole situation is a big farce," said one resident, who gave his name only as Abu Mohammed, or father of Mohammed. "I think the situation will return to normal again but the problem will never be solved. Gangs, smugglers and corrupt people will go back to doing what they were doing before."