The report also calls for the US to begin withdrawing its combat troops from Iraq by early 2008.
George Bush, the US president, has said he will not ask Iran to join regional talks unless it suspends its nuclear programme.
"Iran is ready to help the administration to withdraw its troops from Iraq," Mottaki said, but his country did not "see such political will yet in the United States".
Nuri al-Maliki, the Iraqi prime minister, has said his country's forces would be able to assume security command by June 2007 - which would allow the US to start withdrawing troops.
US and Iraqi officials at the conference were sceptical about any Iranian help for US troop withdrawal.
"I don't know how Iran can help the United States withdraw from Iraq peacefully. They should define that ... What about the Iraqis? Nobody asked them," said Saadoun Dulaimi, an adviser to al-Maliki.
Washington, however, blames Iran and Syria for inflaming the conflict in Iraq.
"The biggest help Iran can make is to stop what they're doing in Iraq right now," a senior US military official said.
"The Iranians are good chess players...and they are going to find a way to prolong this effort and help discredit the United States...to gain more influence and possibly work on their nuclear programme," he said.
Mottaki said the regional chaos sparked by the Bush administration's twin wars in Iraq and Afghanistan showed that military force was no longer a realistic policy option.
"Today the time of threats is over. The period of unilateralism is over," Mottaki said.
"Look at Iraq. Look at Afghanistan. That gives us a very important lesson."