Ali al-Dabbagh, an Iraqi government spokesman, said that al-Maliki would discuss with fellow leaders in Iran, including president Mahmoud Ahmadinejad, the "principle of no interference in internal affairs" during his two-day visit.
"The purpose of the visit is to discuss political and security issues," al-Dabbagh said.
The visit to Iran was due to take place on Monday but will now be delayed for a day or more, Iraqi and Iranian officials said on Sunday.
Mohammad Majid al-Sheikh, Iraq's ambassador to Iran, told Iranian state television: "It was scheduled that he arrive in Tehran tomorrow, but due to some technical reasons he cannot come tomorrow."
Though al-Maliki has brought Sunnis into his national unity government since he took over in May, and conspicuously chose Sunni Gulf Arab states for his first foreign trip, his visit to powerful Iran is likely to upset Sunnis.
Analysts have pointed out that Iran's increasing influence in post-war Iraq since the empowerment of its Shia majority.
This influence, analysts say, is particularly strong in the mainly Shia south, where a Shia leader this week renewed demands for an autonomous Shia region.
Iraq and non-Arab Iran fought a war in the 1980s under Saddam Hussein's Sunni-dominated rule, but ties have warmed since Iraq's Shia won elections, unsettling Iraq's Sunni Arabs and many Sunni-dominated states distrustful of the influence of Tehran's Shia clerical establishment.
The United States, pushing for international sanctions against Tehran over its atomic ambitions, accuses Iran of providing logistical and financial support to Shia militias in Iraq, something Tehran denies.
"Iran views Iraq as its own backyard and has now superseded the US as the most influential power there; this affords it a key role in Iraq's future," a report by the London-based Chatham House think-tank said last month.
It also said that Tehran had an "unparalleled ability to affect stability and security across most of the country".
"Iran views Iraq as its own backyard and has now superseded the US as the most influential power there; this affords it a key role in Iraq's future"
Chatham House report
The announcement of al-Maliki's visit follows a dispute between the two countries in which Iranian border guards this week detained Iraqi guards after accusing them of crossing into Iran.
Ibrahim Shaker, Iraqi defence ministry spokesman, said that the Iraqi patrol, consisting of five soldiers, an officer and a translator, had simply been doing "their duty".
While struggling to defeat factions opposed to the US-backed Iraqi government, al-Maliki has also pledged to rein in Shia militias blamed for much of the sectarian violence that kills an estimated 100 people a day.
Analysts have said disarming militias will be difficult because of their ties with political parties. The Badr Organisation, the armed wing of the powerful SCIRI party, a partner in al-Maliki's coalition, was a product of Iran's Revolutionary Guards.
Meanwhile, a big Shia festival passed off peacefully amid fears of possible violence that brought thousands of troops and police into the holy city of Karbala.
Hundreds of thousands of Shia pilgrims, who had converged in Karbala to celebrate the Shaabaniya ritual, began leaving the southern city after Saturday's climax ended days of chanting, praying and feasting.
The festival passed off peacefully
amid fears of violence
A heavy presence by police and Iraqi troops appeared to have kept out bombers who have disrupted previous rituals. The provincial governor said three million people attended.
Worshippers heard SCIRI leader Abd al-Aziz al-Hakim repeat demands for legislation to let mainly Shia regions of the oil-rich south merge into an autonomous federal region that would neighbour Iran.
In fresh violence on Saturday, 16 bodies, all bound, blindfolded, and shot, were found in different areas of Mahmudiya, south of Baghdad. Police said they were unable to identify them because they were not carrying identity cards.