The apex court said in an order that Gilani should write a letter to the Swiss authorities without waiting to seek the advice of his legal experts.
It asked him to file a report giving details of the action taken by him at the next hearing.
A seven-judge bench led by Justice Nasir-ul-Mulk said contempt proceedings initiated against Gilani for failing to act on the court’s earlier orders to revive the cases against Zardari would continue simultaneously.
The bench asked Gilani to record his detailed response to the contempt proceedings by March 21, failing which final arguments in the case would get underway.
The bench issued this direction after Attorney General Anwar-ul-Haq, the prosecutor for the case, cross-examined Cabinet Secretary Nargis Sethi, who is appearing as a witness.
Emerging from the hearing, Gilani's lawyer Aitzaz Ahsan told reporters that the bench had asked the premier to submit a detailed statement by March 19 or to appear in person and record his statement on March 21.
"If he (Gilani) does not submit a statement, arguments will commence on March 21. If he makes a statement, the final arguments will begin from March 21," Ahsan said.
The Supreme Court recently indicted Gilani for contempt of court after he refused to act on orders to reopen cases of alleged money laundering against President Asif Ali Zardari in Switzerland.