Tehran on Wednesday condemned a planned move by Washington to remove an Iranian opposition group based abroad, the People's Mujahedeen of Iran, from its blacklist of designated terrorist groups.

"The United States' double standard in dealing with terrorism and instrumental use of these groups for political gain is not a new issue," foreign ministry spokesman Ramin Mehmanparast was quoted as saying by state media.

"If the US government goes ahead with this move, then it will be accountable for the blood of thousands of Iranians and Iraqis spilt by this cult... and it weakens world efforts in combatting terrorism," he said.

The US is poised to remove the group, also known as the Mujahedeen-e-Khalq (MEK), from the list of terrorist groups, US lawmakers said on Friday.

The move comes just days ahead of an October 1 deadline set by a US appeals court by which Secretary of State Hillary Clinton had to decide on the fate of the group.

The MEK, whose leadership is based in Paris, has invested much money and years of intense lobbying to be taken off the list.

The leftwing group was founded in the 1960s to oppose the shah of Iran, and after the 1979 Islamic revolution that ousted him it took up arms against Iran's clerical rulers.

The MEK says it has now laid down its arms and is working to overthrow the Islamic regime in Tehran through peaceful means.

It has no support in Iran itself, and no connection to domestic opposition groups.

The chief of Iran's judiciary, Ayatollah Sadeq Larijani, was quoted by his official website (dadiran.ir) as saying that "the leaders of this group must be handed over to the Iranian people and government and be put on trial and receive their punishment."

He added that "the American government and their allies should know this... terrorism may exist anywhere and no country is immune to the dangers of terrorism."

President Mahmoud Ahmadinejad, currently in New York for the UN General Assembly, also spoke of the issue in a meeting with a group of American academics this week, according to the presidency website (presidency.ir).

"Removing them (the MEK) from terrorist groups list, smacks of a double standard," he was quoted as saying.

Ahmadinejad added that the group was behind the killing of "more than 16,000 Iranian citizens and assassinated a number of very popular Islamic Republic officials."

The United States designated it a "foreign terrorist organisation" in 1997, putting in a category that includes Al-Qaeda, the Palestinian Hamas and Lebanon's Hezbollah.

The State Department deems the MEK responsible for the deaths of Iranians as well as US soldiers and civilians from the 1970s into 2001.

The MEK's delisting would end a complex legal battle fought through US and European courts.

Britain struck the group off its terror list in June 2008, followed by the European Union in 2009.

In June this year, the US Court of Appeals in Washington said that if Clinton did not decide whether to deny or grant the group's request to be delisted within four months, it would issue a special writ and remove the group itself.