A series of bombs, meanwhile, targeted Iraqi security forces in Baghdad, providing a grim reminder of the war that President-elect Barack Obama has promised to end. At least 10 people died, officials said.
Despite near-daily attacks, violence is down sharply in Iraq, even as it climbs in Afghanistan, where Obama has promised to refocus U.S. efforts. Biden met with Iraqi President Jalal Talabani but made no public statement.
In Washington, President George W. Bush said he did the right thing in sending an additional 30,000 American troops to Iraq to lower the level of daily violence and to stabilize life.
"The question is, in the long run, will this democracy survive, and that's going to be a question for future presidents," he told reporters.
Monday's violence began when two vehicles parked about 50 yards apart exploded in quick succession as a police patrol passed a bakery in a mainly Shiite area.
The road, which runs through a commercial district, is frequently used by police and army convoys in the eastern New Baghdad neighborhood, residents said.
Police and hospital officials said four people, including a policeman who died at the hospital, were killed and nine others wounded.
"I rushed out with others to see three bodies on the ground in pools of blood," said Mohammed Nasir, 55, who runs a food takeaway shop in New Baghdad. "This place has witnessed several bombings before and we fear that violence will come back after a period of quiet."
The U.S. military said the Iraqi police were hit when explosives planted on a truck detonated as they were responded to the initial car bomb. The U.S. military gave a lower casualty toll, saying one Iraqi policeman was killed and two civilians were wounded.
In western Baghdad, a roadside bomb struck a military convoy with a truck carrying weapons in the mainly Sunni area of Yarmouk, killing three Iraqi soldiers and wounding four bystanders, police said.
Two other roadside bombs apparently aimed at Iraqi army and police patrols elsewhere in the capital killed three people and wounded six others, police officials said.
The Iraqi officials all spoke on condition of anonymity because they weren't authorized to release the information.
The U.S. military confirmed that three Iraqi soldiers also were killed in Baghdad but said it had no other deaths reported. Casualty tolls frequently differ due to the chaotic aftermath of attacks in Iraq.
Iraqi security forces have been frequently targeted as they increasingly take the lead in military operations. U.S. troops are assuming more of an advisory role and preparing to withdraw from Iraq by the end of 2011.
Also Monday, the U.S. military announced that a U.S. soldier died the day before of a non-combat related injury near Samarra north of Baghdad. No further details were released.