The Umma Party claims to have collected 350,000 signatures supporting the expulsion the US embassy from the Republican Palace in the Green Zone, and on Monday extended the deadline for their petition drive to May 2.
"The number of Iraqis who so far have joined the campaign reached 350,000," Fareq Hadi, a party senior member, told the independent news agency Voices of Iraq (VOI) over the phone.
The official expected that the number would exceed one million by the date set for the end of the campaign.
"We will continue the campaign till the parliament recognizes our demand, as we find a wide-scale support by Iraqi citizens," the official added.
The head of the Umma Party, MP Mithal al-Alousi, called for the signature-gathering campaign in late March, arguing that the Republican Palace was a symbol of Iraqi sovereignty, making it inappropriate for it to permanently house a foreign delegation.
The day after calling for the relocation of the US embassy in a radio interview, Alousi's house in the Green Zone was raided by US forces.