Iraq's prime minister used a visit to Tehran on Sunday to soothe Iranian concerns that negotiations between Baghdad and Washington on a new military agreement will lead to permanent U.S. bases across its border.

"There is nothing in today's Iraq which could threaten the stability of the neighbouring countries," Prime Minister Nuri al-Maliki said in a speech at the Iraqi embassy in Tehran.

Iraq, which fought an eight-year war with Iran in the 1980s, is negotiating with the United States on a new agreement aimed at giving a legal basis for U.S. troops to stay in Iraq after December 31, when their United Nations mandate expires.

U.S. officials have accused Iran of seeking to derail the talks by "inspiring" media reports that the United States is trying to force Iraqis to accept a deal on permanent bases.

Ryan Crocker, U.S. ambassador to Iraq, where many people harbour similar suspicions about American intentions, has rejected the reports as "flatly untrue".

Iran, whose nuclear programme has raised tensions with the United States, is opposed to the presence of U.S. troops in Iraq and blames them for the wave of violence that followed the U.S.-led invasion in 2003.

"Iran will always be on the side of the popular government of Iraq," the state news agency IRNA quoted First Vice-President Parviz Davoudi as saying in talks with Maliki on Sunday.

"Helping the establishment of security in Iraq has always been one of Iran's main policies," he said.

Iraqi officials and the United States say Iran is arming, funding and training Shi'ite militias in Iraq, a charge Tehran has always denied.

Iraqi government spokesman Ali al-Dabbagh said before the start of Maliki's three-day visit that the issue of Iranian interference in Iraq's internal affairs would be raised.

Maliki has appointed a committee to investigate the allegations of Iranian meddling and compile a dossier of evidence. It was not clear whether this was discussed during Maliki's meetings with Iranian officials on Sunday.

IRNA quoted Iranian president Mahmoud Ahmadinejad as saying in talks with Maliki: "Iraq's neighbours have more responsibility to help the country to establish peace and security."

A statement issued by Maliki's office after his talks with Davoudi said the two men had discussed measures to improve political, economic and trade relations as well as steps to support the electricity and services sectors in Iraq.

"Iraq is looking forward to Iranian companies taking part in developing its infrastructure," the statement quoted Maliki as saying.

Ties between Iran and Iraq have improved since Saddam Hussein, a Sunni Arab who led Iraq into the 1980-88 war against Iran, was ousted in the 2003 U.S.-led invasion and a Shi'ite-led government came to power in Baghdad.