By North-west correspondent Alex Stevens

Liverpool have made a contract offer to Joel Matip in a bid to prise him from Schalke in the summer, Football Insider sources understand.

The Merseysiders are on the trail of the centre-back, whose agreement with the Bundesliga club expires in the summer.

A Liverpool source has told Football Insider that the club have offered Matip a lucrative deal as they attempt to steal a march on rival suitors.

Manager Jurgen Klopp has sanctioned a move for the Cameroon international, who has come through the ranks at Schalke and is well known to the German from his time in the Bundesliga.

Matip, 24, is out of contract in Gelsenkirchen and is said to be keen for a new challenge.

Klopp has already signed Steven Caulker on loan from QPR until the end of the season after his hand was forced by injuries to Liverpool’s four senior defenders.

Caulker came off the bench to make his debut for the Merseysiders in their thrilling 3-3 draw against Arsenal at Anfield ok Wednesday night.

It is not known if Liverpool will make a permanent move for Caulker but the club is working on options to strengthen their backline.

Schalke want Matip, who has 27 caps for his country, to pen a new deal but that is looking increasingly unlikely.

Matip has remained a regular for Schalke this season, making 22 appearances for the Bundesliga side.