BAGHDAD, Iraq (CNN) -- The leader of a prominent group representing tribes in southern Iraq is calling for "the eviction of the Iranian regime from our homeland."
Iraqi Prime Minister Nuri al-Maliki, left, and Iranian President Mahmoud Ahmadinejad meet in August.
Sheik Jasim al-Kadhim, president of the Association of Nationalist and Independent Iraqi Tribes from the south, condemned what he called Iran's meddling in Iraq by those affiliated with Quds Force, an arm of the Iranian Revolutionary Guard.
The United States accuses the Quds Force of aiding Shiite militias in Iraq and has designated it as a terrorist group.
Al-Kadhim, speaking by phone Friday, said evicting the Iranian regime -- in particular from the southern Iraqi provinces -- is "the only solution and hopeful prospect for Iraq."
Al-Kadhim's comments represent another kink in the relationship between the two nations, who share the Shiite faith and whose friendliness toward each other has raised U.S. concerns.
Additionally, 300,000-plus Iraqi Shiites signed a petition calling for an end to what they call "Iranian terrorist interferences" and demanding the United Nations investigate the Islamic republic's involvement in Iraq.
The United States has been at the forefront of a bitter battle over Iran's nuclear program. Washington suspects Iran intends to develop nuclear weapons, but Tehran has said its program has only peaceful aims.
On Tuesday, the Iraqi Shiite groups announced they had completed the six-month process of gathering signatures for the petition. Watch what Tehran has to say about its nuclear aspirations »
The groups demand the United Nations "dispatch a delegation to investigate the four years [of] crimes in the southern provinces by the Iranian regime and its proxies," according to the Independent National Tribal Organization in Southern Iraq.
The petition has the support of 14 clergy members and 600 sheiks as well as the signatures of 25,000 women, the release said.
"The most painful stab on the back of the Shiites in Iraq by the Iranian regime has been its shameful abuse of Shiite religion to achieve its ominous ends," the petition said.
The People's Mujahedeen Organization of Iran -- or Mujahedeen-e Khalq -- which seeks to overthrow the Islamic regime in Iran, also backs the petition.
The organization has been labeled a terrorist group by the United States, Iraq and Iran -- all for different reasons -- but it continues to operate in Iraq under the U.S. military's protection. The United States considers the group a source of valuable intelligence on Iran.
Iran has blamed the group for supporting Shiite insurgents, but the organization has said "these allegations are only to cover up the crimes of the Iranian regime and its mercenaries in Iraq," according to the Shiite group's statement.
Another Iran-Iraq tiff emerged this week when Iraqi spokesman Ali al-Dabbagh announced upcoming talks that he said will "help to establish security and stability in Iraq and to dispel the tensions in the region."
According to Iran's Press TV, Iranian Foreign Ministry spokesman Mohammad Ali Hosseini expressed concern about some of al-Dabbagh's remarks.
"Al-Dabbagh earlier said that as Iran had cut its support for insurgents in Iraq, Tehran and Washington should take advantage of the situation to hold a new round of talks," the report said. "Hosseini vehemently dismissed the accusations, calling on the Iraqi government not to be influenced by the [psychological war] waged by the U.S."
Al-Dabbagh's office then expressed "surprise and regret" at Hosseini's comments.
In the 1980s, Iran and Iraq fought a nearly decadelong war that left more than 1 million dead. The two countries have been working to improve ties since the U.S.-led invasion ushered in a Shiite-dominated government.
No date has been set for the expert-level talks, which will follow three earlier meetings between U.S. and Iranian officials in Baghdad. But Iranian Foreign Minister Manouchehr Mottaki said another round of talks will occur in "the near future," according to the state-run Islamic Republic News Agency.
The United States and Iran have not had diplomatic relations since 1980, and the Swiss Embassy represents U.S. interests in Iran.
Some signs suggest tensions are easing: Iraqi and U.S. officials have indicated recently that Iran is using its influence to improve security in Iraq by restraining cross-border weapons flow and militia activity, and U.S. commanders released nine Iranian prisoners in Iraq this month. E-mail to a friend
CNN's Thomas Evans, Charley Keyes and Mohammed Tawfeeq contributed to this report.