TEHRAN, Iran -- Iran's president made another bold move Saturday in his power struggle with rival hard-liners by firing three key Cabinet ministers and bypassing several steps that require parliamentary approval.

The dismissals are an apparent attempt by Mahmoud Ahmadinejad to send a message of defiance to critics in parliament, who are now emboldened after Ahmadinejad lost a humbling confrontation with Iran's supreme leader.

A new law requires Ahmadinejad to trim his government from 21 to 17 ministries. Parliament has pushed for the restructuring of the government, which lawmakers say is oversized.

But Ahmadinejad bypassed the legal channels of parliament review for downsizing the government and made the cuts himself without parliament's approval.

Firing the three ministers paves the way for merging several ministries, but plans for the restructuring were supposed to have been drawn up first and approved by parliament.

State radio reported that the three dismissed Cabinet members were Oil Minister Masoud Mirkazemi, Welfare and Social Security Minister Sadeq Mahsouli and Industry Minister Ali Akbar Mehrabian. All are Ahmadinejad loyalists.

The move suggested another high-stakes political maneuver by Ahmadinejad, who claims he doesn't need lawmakers' approval on how he would trim the Cabinet posts. By dismissing allies, it appears Ahmadinejad seeks to show his independence from parliament and take a gamble that lawmakers will not accept the firings.

Ahmadinejad and his backers are struggling to regroup after a stinging public rebuke by Supreme Leader Ayatollah Ali Khamenei over Iran's intelligence minister, whom Ahmadinejad wanted off his Cabinet. The supreme leader ordered him reinstated.

The showdown was interpreted as further evidence of a growing rift between Ahmadinejad and the ruling theocracy and a sign that Khamenei is seeking to tighten his grip on political affairs before parliamentary elections next year and a presidential election in 2013 that will choose Ahmadinejad's successor.

Sensing his vulnerability, rivals in parliament are raising more challenges to Ahmadinejad, including calls to bring him before the chamber for questioning over his policies and alleged constitutional violations.

Prominent lawmaker Ahmad Tavkoli said the parliament will take Ahmadinejad to task for bypassing constitutional requirements over restructuring ministries after lawmakers reconvene from their spring break.