Gilani's remarks revive speculation that he would rather risk losing his job than capitulate in a two-year showdown with the judiciary that culminated last month with him being charged with contempt by the Supreme Court.
He has always insisted that President Asif Ali Zardari is immune from prosecution as president and says the cases against him are politically motivated.
"If I write a letter it will be a violation of the constitution, which is treason and which carries the death sentence," Gilani told PhD students in central Punjab province, with a few in the audience shouting "do not write, do not write".
"If I don't write, I will be convicted for contempt, the punishment for which is six months' imprisonment," Gilani said.
"It's better to face six months' imprisonment than face the death sentence."
Copyright AFP (Agence France-Presse), 2012