The Supreme Court in Pakistan has set up an inquiry into a memo that asked for US help in curbing the powers of the military.
The court said a panel of four high court judges would conclude its findings within a month.
The scandal concerns a note sent from Pakistan's political leadership to US Admiral Mike Mullen, via a former ambassador.
President Asif Ali Zardari's aides deny any links with the document.
The BBC says civilian leaders were worried that the army was about to launch a coup after Osama Bin Laden was killed by US forces in Abbottabad in May.
Correspondents say Friday's ruling will put additional pressure on the government and could even lead to President Zardari's fall from power if a link is established.
Earlier this week President Zardari accused Chief Justice Iftikhar Chaudhry of failing to investigate the murder of his wife, former Prime Minister Benazir Bhutto.
He was addressing party supporters on the anniversary of Ms Bhutto's killing.