The soldier died in a bomb attack in the town of Ramadi, 100 km west of Baghdad, on Tuesday morning.
A US military spokeswoman said two soldiers were injured in the attack when three synchronised bombs blew up near a convoy.
And in a separate incident an American soldier was wounded in a rocket-propelled grenade attack on a military convoy near the flashpoint Iraqi town of Fallujah.
A witness said the attack happened when a convoy of six military vehicles approached a bridge in Fallujah on Tuesday afternoon.
Farmer Rabih Mushraf said the vehicles stopped momentarily before the bridge and then a bomb went off under a truck.
A US soldier fell to the ground and was lifted up by his comrades, but Mushraf could not say how seriously he was injured.
The convoy headed back in the direction of the US base at nearby Habbaniya as residents flocked to the site, chanting, "With our soul, with our blood, we will redeem you Iraq".
The US army could not immediately confirm the incident, but Fallujah has been the scene of frequent resistance attacks on US occupying troops.
Dies in sleep
Another US soldier died on Tuesday while sleeping at a camp in the town of Ramadi, 100 km west of Baghdad, Central Command (Centcom) said, in the second such incident in four days.
"A soldier attached to the 3rd Armoured Cavalry Regiment died while sleeping at a base camp in Ramadi on August 12," Centcom said in a statement.
"The incident is under investigation," it added without giving further details.
Centcom last Friday reported that a Fourth Infantry Division soldier died while sleeping at his base in the town of Kirkuk near the northern Iraqi city of Mosul. No details were provided in that case either.
The latest death takes to 61 the number of US soldiers who have died in non-combat incidents since the White House declared major combat operations in Iraq over on 1 May. At least 58 others have been killed in resistance attacks.
Central Iraq is a hotspot
for resistance attacks
Meanwhile, former members of Iraq's once-dreaded secret police have warned they will take up arms against occupation forces if they are not paid their salaries.
Around 50 ex-members of the Mukhabarat (secret police) picketed the Civil Affairs office in Baquba, near Baghdad, on Tuesday hoping to get cash from the forces which put them out of work.
"We haven't had a penny in five months, we have families to feed," said one of the protesters, lieutenant Muder Khalaf.
He warned that if their demands are not met "we will not let the Americans sleep in peace."
He added: "We are trained in all types of weapons and we're ready to use them if this goes on."
Baquba, 66 kilometres northeast of Baghdad, is a regular battleground for US troops and resistance fighters.
However, the Americans have cast doubt on the protesters' credentials.
US civil affairs officer Captain Dennis Van Wey said the Mukhabarat were responsible for torturing and killing Iraqis, although the protestors denied this.
However, Van Wey acknowledged the protest presented the "potential for significant violence," but said the demonstrators demands will not be met.
The secret police "was dissolved ... they no longer exist, so we are not going to give them salaries," Van Wey said.
But he added talks were under way to try to get some financial aid to the families of these men whom "nobody wants to hire."
The US occupation administrator for Iraq, Paul Bremer, abolished Saddam's 400,000-strong military and labyrinth of security and intelligence services in May.
But former soldiers were paid compensation after they threatened to take up weapons against the US occupation if their salaries were not handed out.