According to Sky Sports, the bid is believed to be around £110 million plus add-ons. However, the total offer did not reach £120 million.
The Premier League champions are now preparing to submit a second offer.
The Magpies are desperate to hold on to Isak beyond this summer and value the striker at £150 million.
Isak is currently in Spain, where he is training alone at his former club Real Sociedad’s training facilities.
The Swede has stayed away from Newcastle’s pre-season tour of Asia, with the club claiming he was recovering from a minor thigh problem.
However, it has become clear that the 25-year-old wants to leave St James’ Park this summer.
