A car bomb struck a U.S. military patrol Saturday in the Iraqi capital, killing two American soldiers and injuring two others, and a Marine died in action in a restive central province, the military said. The man expected to become Iraqi's new prime minister said the coalition government could be formed within days.

"God willing, the government could witness its birth in the coming few days," said Ibrahim al-Jaafari (search), a top member of the Shiite Muslim alliance that won the most parliamentary seats in Iraq's Jan. 30 balloting.

The bloc has said it plans to stand al-Jaafari for the premiership.

Since holding their first session March 16, lawmakers repeatedly have postponed a second meeting because of ongoing negotiations over the makeup of the government.

Al-Jaafari empathized with citizens irritated by protracted negotiations concerning the allotment of Cabinet posts, but he said speed was being sacrificed for a solid agreement with an ethnic Kurdish bloc, expected to help form the incoming governing coalition.

"There are various groups and we're keen that the process of forming the government be quick," he said. "But we're also keen that this birth has all the requirements needed for success."

Al-Jaafari did not specify when the government could be formed.

Other top negotiators have said the assembly could convene again as early as Monday.

The interim deputy prime minister, Barham Saleh (search), said Friday that negotiators were intensifying efforts to bring in the country's Sunni Arabs, believed to form the core of Iraq's rebellion.

The names of the U.S. troops slain Saturday were not immediately released, and no other details were given on the car bombing.

The military also announced Saturday that a Marine was killed a day earlier in strife-torn Anbar province, a heavily Sunni Arab region west of Baghdad that contains the flashpoint cities of Fallujah and Ramadi.

No further details were given concerning the Marine, assigned to the 1st Marine Expeditionary Force.

As of Friday, at least 1,524 members of the U.S. military had died since the beginning of the Iraq war in March 2003, according to an Associated Press count.

Also Saturday, a senior Iraqi defense ministry official said Iraqi troops backed by U.S. forces detained 121 suspected insurgents and uncovered a massive weapons cache — including car bombs, mortar rounds and machine guns — during a joint raid at Musayyib, south of Baghdad.

Neither a U.S. military spokesman nor an Iraqi Defense Ministry spokesman was able to confirm the operation at Musayyib, 40 miles south of Baghdad.

Some of the suspected guerrillas planned to attack Shiite Muslims expected to head in the coming days to an annual religious celebration in the nearby city of Karbala (search), the official said on condition of anonymity.

There were no injuries to any U.S. troops or Iraqi security forces, the official said, and no word on any casualties among the suspected insurgents.

Earlier, military officials said they had discovered a 600-foot tunnel leading out of the main prison facility for detainees in Iraq. No one had escaped, Army spokeswoman Maj. Flora Lee said. She did not know when guards discovered the tunnel.

Camp Bucca holds 6,049 detainees, nearly two-thirds of all those in Iraq, Lee said late Friday. The prison, situated near the southern city of Umm Qasr (search), it is one of three detainee facilities in Iraq.

A bucket cut from a water container and a shovel made of tent material were used to dig the tunnel, Lee said. The opening was under a floorboard of the compound and was concealed with dirt.

Authorities in charge of the compound realized a tunnel was being dug after they found dirt in latrines and other places, Lee said.

"There have been a few other attempts at digging a tunnel but nothing of this size," she said.

U.S. guards fired on prisoners during a riot at Camp Bucca (search) on Jan. 31, killing four detainees and injuring six others.

Insurgents trying to undermine the formation of a new government, meanwhile, seemed to intensify their attacks, carrying out four suicide car bombings that killed 17 Iraqi security officials and two civilians. Militants have stepped up attacks against Iraqi police and soldiers who are key to an eventual U.S. withdrawal.

Twin suicide car bombings Friday in Iskandriyah, 30 miles south of Baghdad, targeted an Iraqi army convoy and police barracks and killed four policemen, two civilians and an Iraqi soldier, police officials said. Eight other members of the security forces and 15 civilians were injured.

Another suicide car bombing Friday targeted an Iraqi convoy south of Baghdad, leaving one Iraqi soldier dead and four others injured, police Capt. Muthama Abdul Rida said.

In Ramadi, where a Thursday bombing killed 11 Iraqi soldiers and injured 14 people, another car bomb exploded Friday. It targeted a U.S.-Iraqi convoy but only killed two attackers.

In Baghdad on Friday, gunmen killed Col. Salman Muhammad Hassan and injured two of his sons as they left a relative's funeral, security officials said. Police also said Friday they found two decapitated bodies clad in Iraqi army uniforms a day earlier on a road north of Baghdad.