In an apparent effort to drive home that point, Prime Minister Nouri al-Maliki told an Iranian envoy that the persistent violence in Iraq — some of it carried out by the Shiite militias Iran is accused of arming — could spill over into neighboring countries, including those that are "supposed to support the Iraqi government."
Al-Maliki's national security adviser, Mowaffak al-Rubaie, said on Sunday that the United States has not provided Iraq with any "solid evidence" that Iran is arming fighters in Iraq.
U.S. Secretary of State Condoleezza Rice is also expected to attend the Iraq conference in the Egyptian resort of Sharm El-Sheik on Thursday and Friday, raising the possibility of a rare direct encounter between high-level U.S. and Iranian officials.
In Washington, Rice would not rule out a meeting with the Iranians, whose delegation will be led by Foreign Minister Manouchehr Mottaki.
"But what do we need to do? It's quite obvious. Stop the flow of arms to foreign fighters. Stop the flow of foreign fighters across the borders," Rice told ABC's "This Week."
Earlier this month, U.S. military spokesman Maj. Gen. William Caldwell said Iranian intelligence operatives have been training Iraqi fighters inside Iran on how to use and assemble deadly roadside bombs known as EFPs, or explosively formed penetrators.
He said Iranian support extended to Sunnis as well as Shiites in Iraq, showing reporters photographs of what he said were Iranian-made mortar rounds, RPG rounds and rockets that were found recently in a Sunni neighborhood of Baghdad.
But al-Rubaie said the United States has not shared any proof with the Iraqi government that Iran is arming insurgents in the country.
"I'm saying this categorically: There is no solid evidence that Iran is supporting or helping al Qaeda in any way," he said in Tampa, Florida, where he is attending a three-day meeting with other international defense leaders at U.S. Central Command headquarters.
Iraqi leaders had been pressing for the Iranians to attend the meeting in Sharm el-Sheik for weeks, but Iran refused to commit, in part because of fears that it would come under pressure from the U.S. and others about its nuclear program.
In addition, the Iranians have been lobbying for release of five Iranians held by the United States in Iraq since January. The United States has accused the five of links to an Iranian Revolutionary Guard unit that arms and trains Shiite extremists in Iraq and elsewhere in the Middle East.
The decision to attend "came after consultations between Iraqi officials and the Iranian president," Foreign Ministry spokesman Mohammad Ali Hosseini said in an interview with Iranian state television.
Senior Iranian envoy Ali Larijani flew to Baghdad on Sunday for talks with al-Maliki and other senior Iraqi officials, the highest-ranking Iranian official to visit Iraq since the collapse of Saddam Hussein's regime in 2003.