Pakistan ended day two 180 runs ahead of England, having lost just two wickets in their second innings.
Vice-captain Cook believes that his side will only claw their way back into the match if they show some "serious guts".
"It will take some serious guts to drag ourselves out of this," Cook told reporters.
"We all know we're a very long way behind in this game. But there are some good players in that dressing room, and I hope we can stand up."
England already trail 2-0 in the three-match series.