The sudden firing of Foreign Minister Manouchehr Mottaki while he was abroad on a diplomatic mission lying for his country is a sign of growing political tension within Iran’s increasingly isolated government. The abrupt sacking of Mottaki, who has served as Iran’s top diplomat since the installation of Mahmoud Ahmadinejad’s government in 2005, is another indication of growing schisms in the ruling establishment, which is under increasing international pressure due to its continued defiance on the nuclear issue. Mottaki has been replaced on an interim basis by the head of Iran’s nuclear program, Ali Akbar Salehi, a strong supporter and key aide to President Ahmadinejad. Mottaki was known to have personal ties to members of Iran’s parliament who have been critical of the divisive Iranian president. Iran’s parliament, dominated by hardliners, increasingly has clashed with the aggressive Ahmadinejad as he has sought to consolidate his own power in the aftermath of last year’s sham elections.

Although Iran’s state-run media gave no reason for the firing, it is likely that Ahmadinejad is making Mottaki the scapegoat for a series of diplomatic embarrassments that the regime has suffered in recent months. Iran was singled out in a U.N. resolution for human rights violations, denied a seat on the U.N. Women’s Rights Panel and blocked from hosting a UNESCO conference on philosophy because of its lack of freedoms. Mottaki also failed to contain the damaging fallout from the revelation of an illegal covert shipment of Iranian weapons discovered in Nigeria in October. Mottaki had clashed with Ahmadinejad last summer, when the firebrand President sought to appoint a group of his own aides as special envoys but was forced to back down after the Supreme Leader, Ayatollah Khamenei, intervened to block the appointments.

Iranian newspapers of all stripes expressed shock at the unexpected purge. An editorial in one hard-line newspaper lamented the fact that the dismissal “will have a negative impact on the Islamic Republic of Iran’s image abroad” and asked: “Could the president not have waited a few hours to sign the letter of dismissal?”

The personnel change is unlikely to bring a substantive change in Iran’s foreign policy because the Foreign Minister acts more as a spokesman than as a policy maker. The real power lies in the hands of the Supreme Leader and his protégé, Ahmadinejad. But the elevation of Salehi, who reportedly was Ahmadinejad’s first choice for Foreign Minister in 2005 before the Supreme Leader instead decided to install Mottaki in that position, indicates that Ahmadinejad remains determined to make the nuclear issue a central pillar of Iran’s foreign policy. As the head of Iran’s nuclear program, Salehi has been one of the strongest advocates of pushing ahead on the nuclear front regardless of international sanctions and he is likely to inject an even harsher tone into Iran’s uncompromising foreign policy.