Maliki's "State of Law coalition won first place in the last legislative elections... (and) any decision that is taken in Iraq and has the support of parliament has Iran's backing," said Deputy Foreign Minister Hossein Amir-Abdollahian.
"If Mr Maliki is chosen as prime minister, we will work hard together. If another person is chosen by parliament, the Islamic Republic of Iran will also support them. It's an internal affair for Iraq," he said.
Maliki, a Shiite, has been prime minister since 2006 and last week vowed to "never give up on" his quest for a third term, despite critics blaming him for steering the Shiite-majority country towards all-out sectarian war.
Shiite-dominated Iran has said it is willing to provide Iraq advice and military assistance in the fight with Sunni insurgents who have now declared an Islamic caliphate.
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The Islamic State (IS) militants overran large chunks of Iraqi territory last month and have declared there own caliphate.
The militant offencive, which led Iraqi troops to abandon their posts, has emboldened Kurdish leaders to press for independence of their autonomous northern region.
"We will never allow (Israeli Prime Minister Benjamin) Netanyahu's dreams about the disintegration of Iraq and the region to come true," Amir-Abdollahian said today.
He added that Iran had warned Iraq's Kurdish leaders against separatism, saying it was "in nobody's interest".
Amir-Abdollahian also criticised the United States for doing "nothing concrete to fight against terrorism".
"At best, the behaviour of the United States over the past three weeks regarding Iraq has been suspect. We see no need to cooperate or have talks with the United States about Iraq," he said.