ISLAMABAD - As a far-reaching constitutional measure aimed at bolstering democracy was tabled in Pakistan's Parliament Friday, an escalating battle between U.S.-backed President Asif Ali Zardari and the country's chief justice threatens the political stability of a key American ally in the war on Islamic extremism.

Some Pakistanis are now accusing Chief Justice Iftikhar Chaudhry, who was the hero of Pakistani democrats when he was reinstated a year ago after a protest movement led by lawyers, of pursuing a vendetta against Zardari.

"There should be accountability of the executive, but since they [the judiciary] appear to be one-sided, the whole issue of accountability gets diluted," said Asma Jahangir, the head of the Human Rights Commission of Pakistan, an independent organization. "These are symptoms of political anarchy. The judiciary is destroying itself."

The standoff between the executive and the judiciary intensified Friday when Attorney General Anwar Mansoor quit, saying the government is "defying" the orders of the Supreme Court.

The Obama administration has invested heavily in Zardari's elected government in Islamabad in the belief that democracy is the best way to combat Islamic extremists in Pakistan.

Washington never backed the movement around Chaudhry, and U.S. officials privately remain skeptical of the chief justice, whom they consider meddlesome and possibly sympathetic to Islamists.