Former enemies Iran and Iraq say they will launch broad military co-operation including training Iraqi armed forces.
Mr Dulaimi is on his first official visit to the Islamic Republic
"It's a new chapter in our relations with Iraq," said Iranian Defence Minister Admiral Ali Shamkhani.
He was speaking at a joint news conference in Tehran with his Iraqi counterpart Saadoun al-Dulaimi.
Relations between the neighbours - who fought a bitter war from 1980 to 1988 - have improved greatly since the overthrow of Saddam Hussein in 2003.
This is the first visit to Iran by an Iraqi military delegation since the war, in which a million people died, started.
The promise of co-operation comes despite repeated accusations by the US - which has about 140,000 troops in Iraq - that Iran has been undermining security there.
"No one can prevent us from reaching an agreement," Mr Shamkhani said when asked about possible US opposition.
Mr Dulaimi echoed his Iranian counterpart's view about a new era of Iranian-Iraqi ties.
"I have come to Iran to ask forgiveness for what Saddam Hussein has done. The same has to be done with Kuwait and all Saddam Hussein's victims," he told the news conference.
Tehran has asked Baghdad not to allow the US to establish long-term military bases on its soil, fearing that it would consolidate what Iranians see as the American and Israeli military domination of the region.
Iran has one of the largest armed forces in the region
But Mr Dulaimi insisted that foreign troops were needed to ensure Iraqi security.
He added: "Iraq will not be a source of insecurity and instability for any of its neighbours. Nobody can use [Iraqi territory] to attack its neighbours."
Among other areas of co-operation, Mr Shamkhani listed mine clearance, anti-terrorism, identifying those still missing from the Iran-Iraq war and training and re-equipping the Iraqi army.
The two ministers said more sensitive issues such as a full peace treaty and war reparations were still a long way from being resolved.
"We have come to our Iranian brothers to ask them for help and we have not yet started on the more sensitive issues," Mr Dulaimi said.
In May Iran's foreign minister promised to tighten security on the two countries' border on his first visit to Baghdad.
An Iraqi government delegation headed by Prime Minister Ibrahim al-Jaafari is expected to visit Tehran next week.