An Iraqi boy cries outside a hospital morgue Wednesday in Baghdad as he waits to collect his relative's body. As many as 15 Iraqi policemen responding to an attack against U.S. bases in Baghdad were killed and 27 wounded when rockets set to be launched exploded before they could be defused, officials said.

Baghdad ? With deadly attacks against U.S. targets increasing around Baghdad, anti-American Shiite cleric Muqtada al-Sadr raised the possibility Wednesday that he may not renew a six-month cease-fire widely credited for helping slash violence.

The cease-fire is due to expire Saturday, and there were fears, especially among minority Sunni Arabs, that the re-emergence of al-Sadr’s Mahdi Army militia could return Iraq to where it was just a year ago – with sectarian death squads prowling the streets of a country on the brink of civil war.

A surge of violence would also make it all the more difficult for Iraq’s Shiites, Sunnis and Kurds to reach agreements on sharing power and wealth, and greatly complicate the debate in the United States on whether and how quickly to withdraw troops.

Rear Adm. Gregory Smith, a U.S. military spokesman, blamed Iranian-backed Shiite extremists for a flurry of rocket attacks – including one Monday against an Iraqi housing complex near the country’s main U.S. military base that killed at least five people and wounded 16, including two U.S. soldiers.

Smith also said one American civilian was killed and a number of U.S. troops and civilian personnel were wounded in a rocket attack in the southeastern area of Rustamiyah on Tuesday night. He did not elaborate, but there is a U.S. base in the predominantly Shiite area.

He said those attacks and another on Tuesday were carried out by “Iranian-backed Special Group criminals,” a term the military uses to describe groups that broke away from the Mahdi Army militia or refused to respect the cease-fire al-Sadr declared in August.

The U.S. military has angered some Sadrists by carrying out raids against breakaway factions. There have been calls from within the militia and its political wing to call off the cease-fire.

The cease-fire has been a key element in a three-piece puzzle that has come together to help reduce violence since mid-2007. The two other factors are the influx of thousands of U.S. troops last summer, and creation of Sunni-dominated groups funded by the U.S. military to fight al-Qaida in Iraq, the most extremist of the Sunni insurgents.

“Al-Sayyid Muqtada al-Sadr’s cease-fire has been helpful in reducing violence and has led to improved security in Iraq. We would welcome the extension of the cease-fire as a positive step,” Smith told The Associated Press, using an honorific reserved for descendants of the Prophet Muhammad.

Sheik Salah al-Obeidi, a spokesman for al-Sadr in the Shiite holy city of Najaf, said that if the cleric failed to issue a statement by Saturday saying the cease-fire was extended, “then that means the freeze is over.”

On an Internet site representing al-Sadr, al-Obeidi said that al-Sadr “either will announce the extension or will stay silent and not announce anything. If he stays silent, that means that the freeze is over.”

Al-Obeidi told the AP that message “has been conveyed to all Mahdi Army members nationwide.”

The ambiguity left many Iraqis uneasy.

“The drop in violence and the quiet which Baghdad witnesses is a clear evidence that this militia was behind all the chaos in the past,” Sunni parliament member Asmaa al-Dulaimi told the AP.

She said ending the cease-fire “will affect national reconciliation and will further deteriorate the security situation nationwide. Resuming their activities, whether against the government or civilians, will lead to a new confrontation with them.”

Smith said that under current conditions, violence was still dropping. He said the number of civilian deaths in Baghdad had fallen from 1,087 men, women and children killed in February 2007 to 178 in the first month of this year.