On the deadliest day for US forces in Iraq, President Bush urged Iraqi voters to defy insurgents and go to the polls on Sunday, while pleading with Americans not to be discouraged by the continuing death toll.
Mr Bush also warned Iran to stay out of the election, and in an ominous development, the Turkish military said it could be drawn into the war if Kurds took control of the city of Kirkuk in the election.
Thirty US marines and a sailor died when a CH-53 helicopter crashed on the Iraq-Jordanian border. Six more were killed in insurgent attacks, the Pentagon said, bringing the US death toll in Iraq to 1,408 since the March 2003 invasion.
"The story today is going to be very discouraging to the American people," Mr Bush told a press conference called at short notice after news of the deaths of 37 US troops and of two dozen Iraqis in explosions and gun attacks. "I understand that. It is the long-term objective that is vital - that is to spread freedom."
The cause of the helicopter crash near the town of Rutba was not revealed, but there was bad weather at the time. Four other Marines died in a rocket attack on a convoy north-west of Baghdad and two other soldiers died in separate attacks. The Iraqi casualties included 15 dead and 30 injured in a car-bomb attack on the headquarters of the Kurdish Democratic Party in the town of Sinjar.
Mr Bush's warning to Iran came in an interview with Al-Arabiya TV in Dubai.
"Let's be clear, the Iranians should not be in a position to influence the elections," he said, reflecting US concern that Shia Muslim Iran will use the elections to influence events in Iraq where Shias are in the majority. Turkey has repeatedly warned that Kurdish control of Kirkuk, a multi-ethnic northern city, would make an independent Kurdish state more viable, which Ankara opposes.
Yesterday Turkish General Ilker Basbug warned that the migration of Kurds to Kirkuk "could make the results of the elections questionable" and pose a security problem for Turkey.
The previous single deadliest incident for US troops was in November 2004 when the collision of two Black Hawk helicopters killed 17 service members. At least 23 US aircraft have crashed in Iraq, with the loss of some 80 troops.
On March 23rd, 2003, the third day of the war, 28 members of the US forces were killed in fighting in Iraq.
Directing his remarks to Iraqis, Mr Bush said: "I urge all people to vote. I urge people to defy these terrorists." He assailed Democrat senators who have criticised the war in US Senate hearings.