ISLAMABAD, May 14 (Reuters) The head of Pakistan's Islamist opposition alliance petitioned the Supreme Court today, calling for the removal of President Pervez Musharraf from office as well as from his position as army chief.

The move by Qazi Hussain Ahmed, president of the Muttahida Majlis-e-Amal (MMA) alliance, came amid a deepening judicial crisis that represents the greatest challenge to Musharraf's authority since he took power in a military coup in 1999.

''We have challenged both of Musharraf's positions because he is not capable of holding either office,'' Shahid Shamsi, a spokesman for Ahmed, told Reuters.

In his petition, Ahmed pleaded that Musharraf be dismissed from the army because he had violated his oath by taking part in politics while remaining in uniform.

He said Musharraf had also disqualified himself from holding the office of president by ''dragging the army into politics''.

Musharraf promised to stand down as army chief by the end of 2004 as part of a deal with MMA but later backed out of his commitment.

Constitutionally, he is due to quit the army by the end of December this year, but is believed to be reluctant to do so.

Musharraf is expected to stand for a second term as president in September or October and wants to be re-elected by the national and provincial assemblies before they are dissolved for elections due around the turn of the year.

Many analysts say Musharraf's move to sack the country's Chief Justice Iftikhar Chaudhry in March might be motivated by a desire to have a more pliable man at the head of judiciary in case of a constitutional challenge to his plans.

REUTERS AB RK1705