Pakistan's attorney general is appearing before the country's Supreme Court to explain why the government has failed to carry out the court's order to open a corruption probe into President Asif Ali Zardari.
The hearing Monday could have profound implications for political stability in the nuclear-armed country.
Last week, the court threatened to dismiss Prime Minister Yousuf Raza Gilani unless he ordered the investigation into a case dating back to the early 1990s.
The government insists Zardari has immunity from prosecution.
The hearing comes against a backdrop of rising tensions between the government and the army, which has carried out three coups since Pakistan was created in 1947.
Last Wednesday, Gilani fired the defence secretary in a dispute over a memo sent to Washington that has enraged the army, escalating a crisis pitting the civilian government against the powerful military leadership.
The army warned darkly of "grievous consequences" as a result of the standoff, which is hampering U.S. efforts to rebuild shattered ties that are needed to negotiate an end to the war in neighbouring Afghanistan.
The tensions have consumed the ruling elite in a country that is struggling to overcome economic turmoil and a bloody al-Qaeda fueled insurgency.