TEHRAN: President Mahmoud Ahmadinejad showed rare defiance of his strongest backer, Iran's supreme leader, by insisting on his choice for vice president Wednesday despite vehement opposition from hard-liners that has opened a deep rift in the conservative leadership.

The tussle over the appointment comes at a time when the clerical leadership is facing its strongest challenge in decades following last month's disputed presidential election.

Supreme Leader Ayatollah Ali Khamenei's top concern appears to be keeping the strong support of clerical hard-liners so he can withstand attempts by the more moderate, pro-reform opposition to erode his authority.

Conservative clerics and politicians have denounced Ahmadinejad's choice for the post of first vice president, Esfandiar Rahim Mashai, because Mashai said last year that Iranians are friends with Israelis. There are also concerns because Mashai is a relative of Ahmadinejad — his daughter is married to the president's son.

Khamenei ordered Ahmadinejad to remove Mashai, semiofficial media reported Wednesday.

Arguing for a further chance to make his case, Ahmadinejad said, "there is a need for time and another opportunity to fully explain my real feelings and assessment about Mr. Mashai."

The president may be digging in because he fears an attempt by hard-liners to dictate the government he is due to form next month.

At the center of the dispute between the president and supreme leader is Mashai, a member of Ahmadinejad's personal inner circle. Iran has 12 vice presidents, and Mashai has been serving in one of the slots in charge of tourism and culture. Ahmadinejad said last week he was elevating Mashai to the first vice presidency. That is the most important of the 12 because it is in line to succeed the president if he dies, is incapacitated or removed. The first vice president also leads Cabinet meetings in the president's absence.

Ahmadinejad is a member of the hard-line camp, but throughout his first term he had disputes over policy and appointments with fellow conservatives, some of whom accused him of hoarding too much power for close associates rather than spreading it among factions.

Most surprising is Ahmadinejad's defiance of Khamenei's order for Mashai's removal. The supreme leader has been the president's top defender in the election dispute, dismissing opposition claims that Ahmadinejad's victory in the June 12 vote was fraudulent. The opposition says pro-reform candidate Mir Hossein Mousavi was the real winner and calls Ahmadinejad's government illegitimate.

Hard-line clerics on Wednesday demanded the president obey Khamenei.

Ayatollah Ahmad Khatami said whether Mashai is immediately dismissed "will test Ahmadinejad's loyalty to the supreme leader."

"When the exalted supreme leader takes a position explicitly, his statement must be accepted by all means and implemented immediately," he said, according to the Mehr news agency. "Those who voted for Ahmadinejad because of his loyalty to the supreme leader expect the president to show his obedience ... in practice."

Ahmadinejad may believe Khamenei's rejection of Mashai is not written in stone and is testing whether he can keep his close associate.

Iran expert Suzanne Maloney pointed out that the supreme leader has not publicly spoken on the issue and reports of his order have been leaked by hard-liners through semiofficial media.

"If Khamenei comes out in Friday prayers calling for (Mashai's) removal, then it would be difficult to imagine Ahmadinejad would refuse that," said Maloney, with the Saban Center for Middle East Policy at the Washington-based Brookings think tank.

Ahmadinejad is "not looking to open his second term by picking a fight with his most important ally in the system," she said.

Khamenei's order to remove Mashai is unusual extension of his powers perhaps a sign he wants to strengthen his position as unquestioned leader in the face of the reformist threat.

As supreme leader, Khamenei has ultimate say in state affairs and stands at the peak of the unelected clerical leadership that under Iran's Islamic Republic can overrule the elected presidency and parliament.

Traditionally, the supreme leader has stayed out of a public role in government appointments. He is believed often to informally vet choices for senior positions behind the scenes, but he does not have a formal role in approving them or an official power to remove them. Even under Iran's 1997-2005 pro-reform government, with which Khamenei clashed, he never overtly ousted any of its officials.

Now Khamenei is facing tests to his authority on two fronts. One is from Ahmadinejad, the other is the open defiance from the reformist opposition, which has continued its campaign against Ahmadinejad despite the supreme leader's declarations that the election dispute is over.

Powerful moderate clerics in the religious leadership under Khamenei have backed Mousavi or declined to recognize Ahmadinejad as the victor. Hundreds of thousands held mass protests in support of Mousavi in the weeks after the election, but were crushed in a heavy crackdown that killed at least 20 protesters and left more than 500 in prison. Still, the opposition has managed to hold two smaller protests since, and is demanding a referendum on Ahmadinejad's legitimacy.

The announcement outraged hard-liners, who have opposed Mashai since he said in 2008 that Iranians were "friends of all people in the world — even Israelis." Mashai also angered many top clerics in 2007 when he attended a ceremony in Turkey where women performed a traditional dance and in 2008 when he hosted a ceremony in which women played tambourines. Conservative interpretations of Islam oppose women dancing.

After days of controversy, Khamenei weighed in. The semiofficial Fars news agency reported Wednesday that Ahmadinejad had been notified of the leader's order to remove Mashai.

The deputy parliament speaker, Mohammad Hasan Aboutorabi-Fard, said late Tuesday that Mashai's dismissal was "a strategic decision" by the system of ruling clerics and he must be removed "without delay," according to the semiofficial ISNA news.

Later Wednesday, Ahmadinejad stuck by Mashai in a speech at Mashai's farewell ceremony from his lower vice presidential post.

"One of virtues and glories God has bestowed to me in life was to get acquainted with this great, honest and pious man," Ahmadinejad said, according to the state news agency IRNA. He said he has "a thousand reasons" to support Mashai and that there was "no convincing" reason for the attacks on his choice.