Baghdad, Iraq ? A car bomb exploded Monday near coalition headquarters, killing four people and wounding 25 in violence that U.S. authorities believe was aimed at blocking the coming transfer of power. Four American soldiers were reported killed in other attacks.

Shiite leaders also urged U.S. troops to halt “aggressive patrolling” in a bid to save a tattered truce with a radical cleric’s militia around Shiite holy cities south of the capital.

Monday’s blast took place in Baghdad’s Harithiyah district, about a half-mile from where the head of the Iraqi Governing Council, Izzadine Saleem, was assassinated in a May 17 car bombing. U.S. soldiers pushed back screaming crowds as ambulances raced to tend to the wounded.

U.S. officers said no prominent political figures were in the area at the time and they were uncertain of the target. It also was unclear whether it was a suicide attack.

However, the dead did include Sabiha Aref, 72, the sister of former Iraqi presidents Abdel-Salam Aref and Abdel-Rahman Aref, who served as head of state in succession between 1963 and 1968. She was killed by flying glass while cooking lunch at home, a relative said.

Four American soldiers died over the weekend in separate attacks, including two killed during fighting in the Shiite holy city of Kufa, where a five-day Shiite-negotiated truce between the Americans and radical cleric Muqtada al-Sadr’s militia appeared to be unraveling.

Hoping to save the cease-fire, Governing Council member Ahmad Chalabi and other Shiite leaders met with al-Sadr representatives and declared there was “a momentum for peace.”

Shiite leaders said Americans should end their “aggressive patrolling” and stay away from holy sites in Najaf and Kufa, Najaf Gov. Adnan al-Zurufi said.

In exchange, those militiamen not from Najaf and Kufa would go home while others would keep off the streets.

“The preliminary agreement is already there,” al-Zurufi said. “We’re waiting for an official response from the high command.”

While the Americans consider the proposal, al-Sadr’s fighters will reduce their visibility in Najaf and Kufa for the next 48 hours, said Ali al-Jhoriafi, an official close to the talks.

The Shiite leaders also hope the Americans will cut back on patrols during the same period.

Coalition spokesman Dan Senor characterized the talks as a step forward even if no deal is reached.

Shiite politicians are trying to end the 2-month-old standoff in the cities 100 miles south of Baghdad and restore government control there.

Troubles emerged in the cities after occupation authorities cracked down on al-Sadr’s militia in April.