Condoleezza Rice, the US secretary of state, insisted that it was up to Iraqis to decide the fate of the former Iraqi president.
She said during a television interview on Monday: "This is not something for Americans or, frankly, Europeans to comment on. I think this is something for Iraqis to decide."
The Iraqi High Tribunal, funded and advised by the US government, found Saddam guilty of crimes against humanity for approving death sentences against 148 Shia civilians after a 1982 attempt on his life.
Rice spoke after Tony Blair, the British prime minister, reaffirmed his opposition to the death penalty for "Saddam or anybody else".
Massimo D'Alema, the Italian foreign minister, described the sentence as unacceptable.
D'Alema said his government, along with the rest of the European Union, opposed the death penalty in principle and feared that executing Saddam would plunge an already deeply divided Iraq "into a veritable civil war".
Saddam's death sentence was also condemned by the European Union presidency, the Vatican, Russia and human rights groups including Amnesty International and Human Rights Watch.
Rice said Europe's stance against capital punishment was "long-standing" and irrelevant to Saddam's case.
She said on Fox News television: "This is an Iraqi process, not an American process or an international process."
In a unanimous decision by the tribunal's five judges, Saddam and two co-defendants were sentenced to death by hanging.
Another defendant was sentenced to life in prison and three others to 15-year jail terms.