The Colombian will arrive on Merseyside once he has completed the international duty with his country.
Liverpool have offered an official bid of initial 40 million euro guaranteed fee, with 25 million euro bonuses FC Porto winger Luis Diaz.
Liverpool beat AC Milan 2-1 at San Siro to seal a record sixth Champions League group stage victory on Tuesday.
The Brazilian goalkeeper wore the armband for Wednesday night’s Champions League victory over FC Porto at Anfield.
The Reds made it five wins from five in Group B after second-half goals from Thiago Alcantara and Mohamed Salah against Porto at Anfield.
Nagelsmann missed Bayern Munich's 4-0 Champions League win over Benfica on Wednesday due to what the club described as a flu-like infection.
AC Milan boss Stefano Pioli said the two games against Porto could be ‘decisive’ for the outcome in the Champions League group stage.
The 20-year-old has started the Reds' last four matches in all competitions, with the standout display being his Man of the Match outing at FC Porto.
Liverpool have started the new Premier League season on a positive note, sitting at the top of the table with four wins from six matches.
Henderson reckons that Liverpool’s emphatic win over Porto is the ideal preparation for Sunday's meeting with Manchester City.