Chaos was also clearly evident in the capital as hundreds of thousands were left without water when a key mains pipe was blown open by more resistance fighters.
It was another black day for the occupying forces struggling to keep law and order.
"A 1st Armoured Division soldier was killed by an explosive device on 18 August in the Karradah district (of the Iraqi capital) at 2pm (1000 GMT)," US Central Command said in a statement.
A CentCom spokesman in Florida refused to go in to details and would only say: "It was a hostile act."
Prior to the latest death, the US army had put at 60 the number of American troops killed in guerrilla-style attacks since US President Bush declared major combat operations in Iraq over on 1 May.
US and British troops killed:
United States 192
United States 93
(US figures relating only to Baghdad and around )
Civilians Between 6096 and 7807
(source: iraqbodycount.net website, drawn from at least two media reports)
The deaths came as the White House blamed the weekend’s crippling sabotage attacks on Iraq’s infrastructure on remnants of Saddam Hussein's regime and "foreign terrorists".
"We are on the offensive. We are going after those remnants of the former regime, we are going after those foreign terrorists," spokesman Scott McClellan told reporters on Monday.
"They will be defeated," the spokesman said as US President George Bush enjoyed a month-long vacation at his beloved ranch near Crawford, Texas.
With summer temperatures hovering around 50 degrees Celsius, up to 300,000 people in Baghdad were without drinking water for a second day on Monday after the sabotage of a key water pipe.
With faltering infrastructure and increasing lawlessness in parts of Baghdad, the water shortage was likely to further wear down Iraqi patience with the occupying US-led forces.
The incident was one of three apparent attacks on civilian and military facilities over the weekend in what is being seen as a new anti-coalition resistance strategy of hitting targets that cause havoc and sow discontent among the population against occupying forces.
On Friday morning, unknown assailants blew up a section of the main northern oil pipeline to Turkey halted the country's essential export of crude.
Attacks on infrastructure are a new resistance tactic
Iraq, currently exporting 700,000 barrels per day (bpd) from its southern oilfields around the port of Basra, has the world's second largest oil reserves.
But bombings and looting have plagued the oil sector since Saddam was toppled in April, with damage to wells leaving just 150 of 700 in working order, officials have said.
Iraq's top oil official, Thamer Ghadhban, said Saturday the sabotage meant Iraq was now losing about 250,000 bpd.
American authorities said it could take weeks to repair the damage and get oil flowing again, hampering hopes of a speedy economic recovery for the war-ravaged country.
Elsewhere, a mortar attack on the notorious Abu Gharib prison on Sunday left six Iraqis dead and 59 wounded.
The coalition forces has signed a contract for the hiring of 6,500 additional security guards to protect oil-related facilities in Iraq, a spokesman told Agence France Presse on Monday.
The Coalition Provisional Authority signed a contract with the Johannesburg and Dubai-based Erinys International security firm to hire and train the guards to protect 100 oil-related installations, the spokesman said, adding the contract had been under negotiation for a few months.
On its web site, Erinys bills itself as a specialist in the Middle East and North Africa, as well as "volatile, uncertain or complex environments."