BAGHDAD &#8212 In mounting bloodshed south of Baghdad, suspected Shiite Muslim militiamen stormed into a Sunni Arab home Tuesday and gunned down seven family members, including a baby being bounced on her mother’s shoulder.

Shadowed by the violence, U.S. Ambassador Ryan Crocker, co-author of a highly anticipated report to Congress next month, said Washington’s blueprint for reconciliation was insufficient to win back control of Iraq. Congressional benchmarks don’t tell the whole story, he said.

Crocker and the U.S. military commander, Gen. David Petraeus, may be heading into a storm of discontent as they argue before Congress that American troops need more time in Iraq.

Last week, a stunning suicide bomb attack killed as many as 500 people in northern Iraq. The gruesome family murder south of the capital Tuesday underlined unabated sectarian violence.

Even President Bush acknowledged frustration with Iraqi Prime Minister Nouri al-Maliki’s leadership during a Tuesday trip to Canada.

Sen. Carl Levin, Democratic chairman of the Senate Armed Services Committee, said al-Maliki should be ousted in favor of a less sectarian and more unifying leader. Levin issued the call shortly after visiting Iraq.

The brutal attack south of Baghdad killed seven members of 70-year-old Khayrallah Salman’s family. He ran a small grocery in Mahaweel, 35 miles south of Baghdad, and died along with six relatives, including the 6-month-old girl, a 12-year-old girl and two women.

A son and daughter-in-law were wounded, said Babil province police Capt. Muthanna Khalid.

A witness said the baby’s mother, who survived, was bouncing the child on her shoulder when the gunmen opened fire after breaking into the house about 8:30 a.m. The witness would not allow use of her name, fearing retribution.

Other witnesses and neighbors said Shiite Mahdi Army militiamen were responsible for the killings of the family, members of the Sunni al-Janabi tribe. Police did not give a motive, and allegations against the militia could not be independently confirmed.

The Mahdi Army, which is nominally loyal to radical Shiite cleric Muqtada al-Sadr, has splintered in recent months as the firebrand cleric has taken refuge in Iran.

Some factions are accused of pursuing a sectarian campaign to rid Baghdad and surrounding areas of Sunnis.

In Baghdad, Crocker spoke to reporters a few days before traveling to Washington to report to the president and Congress. He called Iraq’s problems difficult but fixable, arguing for more time for his diplomacy and operations by the bolstered American military force.

“Failure to meet any of them [congressionally mandated benchmarks] does not mean the definitive failure of the state or the society,” Crocker said.

“Conversely, to make them all would not by any means mean that they’ve turned the corner and it’s a sun-dappled upland from here on in with peace and harmony and background music. It’s just a lot more complex than that.”