Hardline Iranian President Mahmoud Ahmadinejad sacked the foreign minister on Monday and appointed the top nuclear official as caretaker to the key post, the official IRNA news agency reported.

'I appreciate your diligence and services as the foreign minister,' IRNA quoted Ahmadinejad as saying in a letter to Manouchehr Mottaki.

Mottaki is considered a close ally of Ahmadinejad's election rival, parliament speaker Ali Larijani, who is locked in a struggle with the president over the relative powers of parliament and the executive.

The change of foreign minister is a sign that the infighting between Ahmadinejad and Larijani is deepening, analysts say.

State television reported that Ahmadinejad had made Ali Akbar Salehi, the head of the Atomic Energy Organization and a close ally, caretaker foreign minister.

IRNA said Salehi will keep his current job while acting as foreign minister. But a source told the semi-official Fars news agency that Mohammad Ghanadi, a senior nuclear official, might replace Salehi in the country's top nuclear post.

A reformist website said Mottaki was dismissed because he had been critical of Ahmadinejad's foreign policy.

'Mottaki failed to adjust himself to the president's viewpoints and his foreign policy,' the website Mardomsalari reported.

The website Khabaronline, which is close to the government, said Mottaki had 'harshly criticized the president for setting up a parallel diplomatic apparatus' by appointing six foreign policy advisers.

Ahmadinejad's government, backed by Supreme Leader Ayatollah Ali Khamenei, crushed the street protests that followed Ahmadinejad's disputed re-election in June 2009.

The vote created a deepening rift among ruling hardliners, some of whom resent the rising economic and political power of Ahmadinejad.

'Salehi was Ahmadinejad's first choice for the ministry in 2005 ... but Khamenei rejected Salehi,' a moderate former official told Reuters on condition of anonymity.

Larijani, a fierce critic of Ahmadinejad's economic policies, has tacitly urged Khamenei to rein in the fiery head of state, to little visible effect.

Prominent lawmakers have warned that they may take legal action against the president, and even impeach him, if he continues to ignore the constitution. Critics say Ahmadinejad is spending petro-dollars without the approval of the assembly.-Reuters