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."