The Reds will pay a maximum of £25million for the Holland international, taking into account various add-ons.
It is believed Wijnaldum's former club PSV Eindhoven are due a sell-on fee for a player who moved to St James' Park a year ago for £14.5million.
Manager Jurgen Klopp has been looking to strengthen his midfield options and turned his attention to Wijnaldum after giving up their pursuit of Udinese's Piotr Zielinski.
Source: PA