Iranian President Mahmoud Ahmadinejad is expected to become the target of a lawsuit which accuses him of inciting genocide against Israel.
Mr Ahmadinejad accuses Israel of trading off a "Holocaust myth"
The suit is expected to be launched by a panel of international lawyers and former diplomats in New York.
The former US envoy to the UN, John Bolton, is backing the move, which is led by the Conference of Presidents of Major American Jewish Organisations.
However, it remains unclear which legal body the suit will be filed with.
The Iranian mission to the UN dismissed the call as "a propaganda move, and an act without any substance", according to the Financial Times newspaper.
Mr Ahmadinejad this week hosted a conference in Tehran questioning whether the Holocaust - the murder of some six million Jews by the Nazis during World War II - actually took place.
The conference, which drew in white supremacists and Holocaust deniers, has been widely condemned.
Mr Ahmadinejad has made a string of fiery statements about Israel, calling for an end to the Israeli state.
Some six million Jews were murdered by the Nazis during World War II
"The trend for the existence of the Zionist regime is downwards and this is what God has promised and what all nations want," he said at the Tehran conference.
Mr Ahmadinejad has also played down the extent of the Holocaust, describing it as a myth used to justify the existence of Israel and oppression of the Palestinians.
Some analysts have dismissed this as pure rhetoric - an attempt by Mr Ahmadinejad to boost his credentials in the Islamic world as a defender of the Palestinians, the BBC's Pam O'Toole says.
But groups like the Conference of Presidents of Major American Jewish Organisations (CPMAJO) disagree, our correspondent says.
They feel that the Iranian president poses a significant threat to Israel and want to see him charged with incitement to genocide.
"We always say 'never again', but here is someone who genuinely poses a threat and nothing is being done," says Malcolm Hoenlein, executive vice-chairman of the body.
"We can't just dismiss him," he says.
'Difficult to prove'
Legal experts attending the meeting are expected to argue that the Iranian president 's comments constitute incitement to genocide and therefore violate the UN Genocide Convention.
But others experts point out that even the much more serious charge of genocide itself is extremely hard to prove in a court of law.
They say this is because the prosecutor must show that the accused was acting with a very specific intent to eliminate a group on the basis of either its ethnicity, religious beliefs or nationality.
"Incitement is a form of the crime of genocide so there wouldn't be any lesser showing, that I'm aware of, as to the definitional components of genocide in order to make a credible case," says Richard Dicker from Human Rights Watch.