Wijnaldum, who has 30 international caps for Holland, is undergoing a medical at the club's Melwood training ground.
Liverpool have offered Wijnaldum a five-year deal with the 25-year-old making his last appearance for Newcastle in their 2-2 draw with Doncaster Rovers on Wednesday night.
The midfielder joined Newcastle in a £14.5m switch from PSV Eindhoven last summer but was unable to prevent their relegation from the Premier League.
Wijnaldum, whose situation was also being monitored by Tottenham, was Newcastle's leading scorer last season with 11 goals, four of them in a 6-2 league demolition of Norwich, although his form was patchy and he was unable to help the club retain its top-flight status following the appointment of Rafael Benitez as manager.
Everton had also been interested in Wijnaldum - with manager Ronald Koeman a big admirer of the player - but no bid has materialised from Goodison Park.
Liverpool could be in the market for midfield reinforcements after accepting a £13m bid from Stoke City for Joe Allen.
The Reds maintained their unbeaten pre-season campaign on Wednesday night as goals from Marko Grujic and Alberto Moreno saw off Huddersfield Town.
DONCASTER ROVERS 2 NEWCASTLE UTD 2 (Hayden, Perez)
Sels, Janmaat (Sterry, 45), Mbemba (Saivet, 65), Lascelles (Dummett, 45), Colback (Hayden, 45), Anita (Gamez, 45), Ritchie (Gouffran, 45), Aarons (Perez, 45), Shelvey (Wijnaldum, 79), Mitrovic (Gayle, 45), Armstrong (Thauvin, 60).
BOHEMIANS 0 NEWCASTLE 6 (Ritchie, Mitrovic, Gayle, Thauvin, Aarons, Wijnaldum)
Sels, Anita, Lascelles, Mbemba, Sterry, Aarons, Colback, Gouffran, Ritchie, Saivet, Mitrovic.
Subs: Darlow, Gamez, Dummett, Wijnaldum, Shelvey, Hayden, Perez, Gayle, Janmaat, Tiote, Thauvin.