All three were from the 1st Infantry Division, according to an army spokesman on Sunday.
Since 31 March, at least 94 US soldiers have been killed in action in Iraq - more than were killed during the three weeks last year when Iraq was invaded and occupied.
However, it appears the figure of 94 may well be an underestimate.
Numerous US marines are believed to have been shot dead and wounded on Saturday in one of the fiercest battles between US troops and Iraqi resistance near the Syrian border.
According to The Post-Dispatch newspaper, at least five soldiers were shot dead and nine seriously wounded after a 14-hour skirmish near the border town of Husayba.
A US defence official would not confirm or deny the report, saying the military was still awaiting reports from the region to get a complete picture.
But the newspaper said dozens of Iraqi fighters were also killed in the day-long battle.
The US-led occupation has
become increasingly resented
According to the report, nearly 300 Iraqi fighters from Falluja and Ramadi launched an offensive early on Saturday by setting off a road-side bomb to lure Americans out of their base.
Resistance fighters then fired 24 mortars as the marines responded to the attack.
The paper said at least nine soldiers were wounded and more than 20 Iraqi fighters were captured.
New battle approaches
Meanwhile, supporters of Shia cleric Muqtada al-Sadr said they expected US forces to attack the holy city of Najaf after mediation efforts failed.
According to the head of al-Sadr's office, Qais al-Khazali, negotiations ended "because the mediators have told us the Americans are putting obstacles towards finding solutions to the crisis and the situation is getting worse.
"We are expecting the Americans to attack Najaf any moment now."
Al-Sadr has been in Najaf, located south of the capital, for more than a week.
US-led occupation forces want him on charges related to the murder of a rival cleric last year, and insist he disband his Mahdi Army militia.
Both al-Sadr and a representative of Grand Ayat Allah Ali al-Sistani - Iraq's most senior Shia cleric - warned coalition troops against entering the holy cities of Karbala and Najaf, calling them "red lines".