Iran said Sunday it supports Nuri al-Maliki's bid to stay on as Iraq's premier but that it is ready to back any other candidate chosen by parliament in Baghdad.
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.
The Iraqi parliament is to convene on Tuesday to elect a speaker, president and prime minister.
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 overran large chunks of Iraqi territory last month and have now declared an Islamic caliphate.
However, Iran's involvement in Iraq appears to be deepening, with the official IRNA news agency reporting on Saturday that an Iranian pilot had been killed while fighting to defend a Shiite shrine in the city of Samarra, north of Baghdad.
The report did not say whether the pilot was killed while flying sorties or fighting on the ground, but his death is thought to be Tehran's first such military casualty since the fightback against the militants began.
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The Islamic State (IS) offensive, which led Iraqi troops to abandon their posts, has emboldened Kurdish leaders to press for independence of their autonomous northern region.
Tehran opposes a break up of Iraq, denouncing it as an Israeli plot.
"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 on Sunday.
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.
Turning to Tehran's regional rival Riyadh, he said the "role of Saudi Arabia in the events of the region, including Syria and Iraq, is not positive."