BAGHDAD, Iraq — In the latest proposal to curb the seemingly unstoppable violence in Baghdad, the Iraqi government is planning to build a defensive barrier around the city to keep attackers out, though it isn't clear whether it will be a trench or a berm.

Iraq's Interior Ministry said Friday that the government wants to dig a trench encircling the capital, but at a news conference in Washington, President Bush said the barrier would be a berm.

"They're building a berm around the city to make it harder for people to come in with explosive devices, for example," he said.

U.S. officials in Washington said they could not explain the discrepancy. In Baghdad, military spokesman Sgt. Jeremy Pitcher said he was sure Bush and the Iraqi government are talking about the same plan.

"I know the Iraqi government said trench, and then President Bush said berm," he said. "There will probably be dirt moving somewhere."

Whether a trench or a berm, however, the defensive plan would be a massive, difficult undertaking. Baghdad's circumference runs to roughly 100 miles, most reconstruction projects are languishing unfinished or unstarted because of security concerns, and the government is still struggling to assert its authority in the capital.

Interior Ministry spokesman Gen. Abdul Karim al-Kinani said the plan to dig a trench is part of the government's security plan to pacify Baghdad, which was initially launched in June. It will be deep and wide enough to prevent cars from crossing, forcing all vehicles to go through the 28 access roads leading into the capital, he said.

"This trench is going to have 28 entrances and is going to be under our forces' control in order to limit the terrorists' access to Baghdad," he said.

Berms have been used as a defensive measure in the past by the U.S. military, which threw one up around an entire village north of Baghdad last year and erected another along much of the Syrian border. U.S. officials say that berm has been successful in restricting the infiltration of foreign fighters into Iraq.

Saddam Hussein favored trenches. He ordered ordinary Iraqis to dig them in their backyards to defend against invading U.S. troops in 2003, and his security forces set fire to oil-filled trenches as the Americans approached.

It is unclear, however, whether any kind of barrier would help to significantly bring down the levels of violence in Baghdad. On a day when 51 bound and tortured bodies were found dumped on the city's streets, bringing to around 130 the number found in the past three days, Sunni leaders accused Shiite militias based inside the capital of carrying out the killings.

As in previous cases, most of the bodies were found bound, tortured and shot in the head. pointing to activity by the mysterious death squads that haunt Baghdad neighborhoods and which Sunni leaders say have ties to the Shiite-dominated Interior Ministry.

Adnan Dulaimi, head of the National Concord Front, the largest Sunni bloc in parliament, called the surge in the body count over the past few days a "catastrophe" and said the government is turning a blind eye to the killings.

"This is being done by the militias who are circling Baghdad's streets while the U.S. and Iraqi forces are doing nothing to stop them," he said. He said he believes that most of the bodies belong to Sunnis abducted over the past two months and that the militias have now decided to kill them and throw them on the streets.

Most of the bombings in Baghdad are carried out by the Sunni-dominated insurgency, and al-Kinani said he is certain the proposed barrier will help reduce attacks because most insurgents are based outside the city.

"Of course, it is going to be 100 percent successful because cars will have no choice other than to go through these 28 entrances, and they will be searched and caught," he said.

The trench — or berm — will be implemented in the third phase of the three-step security plan launched June 15 by the Iraqi government, he said. In the first phase, extra checkpoints were set up around the city, but the rate of killings only increased.

The second phase began in early August and involved the deployment of additional U.S. troops to search and clear troubled Baghdad neighborhoods, mainly in the predominantly Sunni west of the city. The third phase is intended to extend the operation into Shiite areas in the east.

Also Friday, the military reported the deaths of three American servicemen, one in Anbar province, one in Baghdad and another the previous day in Baghdad, bringing to five the number who died Thursday. In addition, a soldier was reported officially missing after Thursday's suicide bombing west of Baghdad that killed two soldiers.