Speaking from her hospital bed where she is being treated, Sgrena told Sky Italia TV it was possible the soldiers had targeted her because Washington opposes Italy's dealings with kidnappers that may include ransom payments.
"The United States doesn't approve of this (ransom) policy and so they try to stop it in any way possible."
She offered no evidence for her claim, but the sentiment reflected growing anger in Italy over the conduct of the war, which has claimed more than 20 Italian lives, including the secret agent who rescued her moments before being killed.
Nicola Calipari, 52, who had led the operation leading to Sgrena's release, was killed as he tried to shield the 56-year-old journalist from gunfire by US troops attempting to stop their car en route to Baghdad airport.
Although Italy has denied paying kidnappers in past hostage releases, Agriculture Minister Gianni Alemanno told the Corriere that "very probably" a large ransom had been paid in this case.
Italian newspapers have speculated that anything up to 8 million euros ($10 million) may have been paid.
'Hail of bullets'
In a report in the Rome-based Il Manifesto newspaper on Sunday, she recalled the shooting, and said the car had come under a "hail of bullets" less than a kilometre from the airport.
US troops had opened fire although the driver had radioed them to inform them of their passage.
US soldiers said the car carrying
Sgrena did not follow instructions
While under fire, she recalled comments made by her kidnappers during her four-week captivity: "There are Americans who do not want you to come back," Sgrena wrote without giving further details.
She also wrote: "Nicola threw himself on top of me, to protect me and then suddenly I heard his last breath as he died on top of me."
In an interview she said she could see "no reason" why the US soldiers had opened fire. She also insisted the car was not travelling at high speed, in contrast to a US military version of the events.
Sgrena's partner had earlier accused US troops of "trying to kill her". Speaking to reporters in Rome, Pier Scolari said US soldiers had intentionally opened fire on the car leading Sgrena away from her captors.
After visiting her in Rome's military hospital, Scolaria said: "Giuliana had certain information and the US military did not want her to leave alive."
The Italian intelligence service rejected Scolari's claims, Italian television reports said on Saturday.
"Giuliana had certain information and the US military did not want her to leave alive"
Guiliana Sgrena's partner
Italian President Carlo Ciampi, meanwhile, has announced that he intends to issue a posthumous decoration to Calipari, the father of two children, recognising his military service.
Italian media reported he was killed by a bullet that struck him in the head.
His coffin was to lie in state in a chapel in central Rome.
Calipari has already been declared a national hero and will be given a state funeral.
Pope John Paul II, who remains in a clinic in Rome following throat surgery, sent a telegram to Calipari's family calling him a "generous hero".
Berlusconi's support for the US in
Iraq is widely unpopular at home
The incident on Friday sparked tension between the US and Italy. A national outpouring of grief and anger put pressure on Berlusconi, an ardent supporter of Bush and his policies, to get answers from Washington on what went wrong.
The US has promised a full investigation into the incident.
The US military says the car was speeding towards a checkpoint and ignored warning shots, an explanation denied by government ministers and the driver of the car.
"We need to get the guilty punished and an apology from the Americans," Alemanno said. "We are trustworthy allies but we must not give the impression of being subordinates."
Right to know
Italy's minister for parliamentary relations, Carlo Giovanardi, has also said he did not believe the US version of events.
"We are trustworthy allies but we must not give the impression of being subordinates"
Italy's Agriculture Minister
"All 57 million Italians who were united in the anticipation of Giuliana Sgrena's liberation have the right to know what happened," Romano Prodi, the former prime minister and leader of Italy's centre-left opposition, said.
Berlusconi summoned the US ambassador immediately after the event and will need to present some answers from Washington when he addresses parliament on Wednesday.
He led Italy into the conflict in Iraq where it has some 3000 soldiers, a decision opposed by a majority of Italians and the opposition which is seeking to unseat him at a general election next year and weaken him at regional polls next month.
In a related development, the Italian prosecution launched a manslaughter investigation into Calipari's fatal shooting, Italian media reported on Sunday.
His body, returned to Italy in the early hours of Sunday draped in the Italian flag and received by relatives, a guard of honour, Berlusconi and President Ciampi, was to lie in state on Sunday following a post mortem examination.
Sgrena sustained a fractured collarbone and facial injuries in the incident, and two other agents were also injured, one seriously.