More than 180 members of the British Parliament joined a similar effort by European lawmakers proposing that the Obama administration shift its stance on Iranian opposition movements as part its new policy of engagement.
"Our experience has shown that the Iran crisis cannot be resolved without an Iranian solution and without relying on its main opposition movement," the letter said.
President Bill Clinton included the PMOI on the U.S. State Department's Foreign Terrorist Organizations list in 1997 following the election of Iranian President Mohammad Khatami.
Though largely targeting Iranian government officials, PMOI's killing of American contractors in Tehran in the 1970s, participation alongside Saddam Hussein's forces in suppressing Kurdish and Shiite rebellions in Iraq in 1991 and later attacks on Iranian embassies in 1992 earned it a spot on the terrorist lists of several nations.
The PMOI and its affiliates in the Paris-based National Council of Resistance of Iran have waged a successful delisting campaign in Britain and Europe, with similar efforts under way in the United States.
In the letter to Obama, lawmakers said they fear a "catastrophic humanitarian crisis" would result from Washington's refusal to delist the group, adding that Iran uses the listing as justification for threats against the PMOI.
"It is time for the U.S. administration to listen to this message, a message brought by you who have proved to be symbols of peace and democracy in today's world," Maryam Rajavi, NCRI president, said in a videotaped statement.