Supporters of an Iranian opposition group demonstrated en masse Friday in Washington to urge the Obama administration to strike the group from a US terrorism blacklist.   Supporters of the People's Mujahedeen Organization of Iran (PMOI), which is also known as the Mujahedeen-e-Khalq (MEK), said "several thousand" of them took part in the rally after having traveled to the capital from 41 US states. However, AFP estimated the number at between 1,000 to 2,000 people. Maryam Rajavi -- the leader of the National Council of Resistance of Iran, the broad grouping that includes the Mujahedeen -- called for the PMOI to be delisted in a video message to the crowd in Farsi, sparking chants of approval. Rajavi is barred from entering the United States. The PMOI was originally designated by the US State Department as a Foreign Terrorist Organization (FTO) on October 8, 1997 during the administration of president Bill Clinton. It has been redesignated in subsequent years, including by the George W. Bush administration, but was removed from the European Union's equivalent blacklist in 2009. Daniel Benjamin, counter-terrorism coordinator at the State Department, said in May that President Barack Obama's administration would decide in six months on whether to strike the PMOI from the blacklist. In December, several officials who had served in Bush's administration -- Tom Ridge, John Bolton, Frances Townsend and Michael Mukasey -- backed delisting the PMOI. The officials said such an approach is needed because the Obama administration's policy of engaging Iran will fail to prevent Tehran from acquiring nuclear weapons. Iran says its nuclear program is purely peaceful. The Mujahedeen set up in Iraq during the 1980-1988 Iran-Iraq war and received support from former Iraqi dictator Saddam Hussein's regime to mount armed attacks against Iran. Following Saddam's overthrow in 2003, they were disarmed by US forces. The United States guaranteed security for their base at Camp Ashraf until handing over authority to Iraqi forces there in 2009. On April 8, 34 people were killed and dozens wounded when Iraqi forces attacked the camp. In addition to asking for the PMOI to be delisted, protesters also demanded Washington ensure protection of their camp.