Survivors of Auschwitz are suing the Allies for failing to prevent the slaughter at the Nazi death camp.
They said Britain and the US knew what was going on there in the spring of 1943 but didn't agree to act until August that year.
They believe more than 400,000 Jews could have been saved in that time, so they are claiming billions of pounds in compensation.
The Auschwitz Committee has launched a case at the US District Court in Washington, where the hearing stands more chance of success.
Florida lawyers behind a similar action against IBM are also involved in the case, according to reports.
They claim the computer company supplied technology to the Nazis which made the final solution possible.
Kurt Goldstein, vice-president of the survivors' committee, said: "For decades we have been dealing with the Germans who were guilty, now it is the turn of the Allies to face up to their responsibilities."