"We will not allow Iraq to become a platform for harming the security of Iran and neighbours," Maliki said after a late-night meeting with Iranian Foreign Minister Manouchehr Mottaki in Tehran.
Maliki's comments come amid Iranian alarm over American pressure on Baghdad to sign an agreement that would keep US soldiers in the country beyond 2008.
Iran has always called for the immediate withdrawal of US troops from Iraq.
US President George W. Bush and Maliki agreed in principle last November to sign the Status of Forces Agreement (SOFA) by the end of July. But Iraq has now said it has a "different vision" from the United States on the issue.
Iran's concern about the deal comes amid renewed tensions over its nuclear programme, which the United States fears is aimed at making atomic weapons, a charge vehemently rejected by Tehran.
The United States has never ruled out a military attack to punish Tehran's defiance while Israel has also been warning there may be no alternative to a strike against Iran.
Maliki, quoted by Iran's state news agency IRNA, said: "Iraq's stability and security can have a great impact on the region … We see the implementation of peace and security in Iraq and Iran as what both countries want."
Iraqi government spokesman Ali al-Dabbagh had said Maliki would be using the visit to assure Iranian leaders that Iraq "will not serve as a base or staging ground to launch attacks against neighbouring countries".
The Shiite premier — on his third visit to Tehran since taking office two years ago — was on Sunday due to also hold talks with other top officials including President Mahmoud Ahmadinejad.
Mottaki, meanwhile, vowed that relations would expand further, saying the Iraqi delegation would "find good ground for creating new strategies in deepening the two countries' ties," according to IRNA.
Iran and Shiite-majority Iraq waged a war between 1980 and 1988 in which around one million people died but ties have warmed considerably since the overthrow of Saddam Hussein's Sunni-dominated regime.
Maliki, who lived in exile in Iran during Saddam's dictatorship, is making his third visit to the country as prime minister. Ahmadinejad's March visit to Iraq, the first by an Iranian president, was also hailed as a landmark in ties.
But some observers expect Maliki in the talks to also raise allegations of Iranian interference in Iraq's affairs, a charge that the predominantly Shiite Islamic republic has vehemently denied.
The United States has accused Iran of shipping in tank-busting munitions for attacks on US troops, training Shiite militants inside Iran for operations in Iraq and supplying rockets for attacks in central Baghdad.
Last month, Maliki also formed a panel of security ministries to weed out any evidence of Iranian interference in Iraq's affairs, a charge that Tehran has vehemently denied.
Washington was troubled by the apparent warmth of ties displayed during Maliki's last visit to Iran in August 2007 and will again be closely watching his latest trip.
US ambassador to Iraq Ryan Crocker stressed in Washington on Thursday that Iran and Iraq were neighbours and had to conduct a relationship. "The question is: what kind of relationship is it going to be?" he said.
