Pakistan's Supreme Court has ordered Prime Minister Raja Pervez Ashraf to appear before it to explain why he has not taken action to reopen corruption investigations against the president.
The move is the latest episode in a long-running standoff between the government and the judiciary.
Two months ago the court found Ashraf's predecessor, Yusuf Raza Gilani, guilty of contempt over the issue and disqualified him from holding the post of prime minister.
The Supreme Court wants the prime minister to write a letter to Swiss authorities asking them to reopen an old corruption case against President Asif Ali Zardari.
The government has resisted having Zardari investigated, arguing that as head of state he has immunity from prosecution.
The head of a five-judge panel, Asif Saeed Khosa, said on August 8 that Ashraf must appear on August 27. Khosa said it was unfortunate that the prime minister had failed to comply with the court order already.
The court had previously given Ashraf until August 8 to write to Switzerland asking it to reopen the multimillion-dollar graft probes.
A pro-government lawyer, Khurram Latif Khosa indicated that the government is ready to tackle the legal challenge:
"The court has given its decision," he said. "It's an interim order. It is not a judgment. God willing, we will wait and see what happens during the proceedings on the twenty-seventh [of August]."
An adviser to the prime minister, Fawad Chaudhry, said Ashraf had been informed about the court ruling on August 8, and he would consult with his political allies before making any decision. Chaudry said the court ruling could further deepen political instability as a time when the country was facing multiple challenges.
A prominent Pakistani lawyer, Abdul Hafeez Pirzada, said Ashraf might also be disqualified from office if he did not write the letter to Swiss authorities, but still did not expect him to do so.
According to political analyst Imtiaz Gul, the civilian government now has to find a compromise.
"I think a lot will depend on whether the government itself tries to find a middle way," he said. "That [involves] writing a letter in a way that fulfills the order of the Supreme Court and also, at the same time, does not affect the interests of the person or the persons who are supposed to be impacted by such a letter."
The court has been aggressive in using its clout to investigate the government as well as Pakistan's security agencies, and appears to consider it unacceptable for the government to ignore its orders.
The ruling Pakistan People's Party views the court with suspicion, and supporters have questioned whether the court is becoming too powerful.
With reporting by Reuters, AFP, and AP