Newcastle are expecting an “official approach” for Alexander Isak this week from Liverpool after they agreed to sell Luis Diaz to Bayern Munich for £65.6 million.Isak did not join Eddie Howe’s squad on their first pre-season stop in Singapore and will not follow them to South Korea this week amid Liverpool’s transfer interest.Newcastle maintain he was left behind due to a thigh injury, although scans came back clear. He has, however, made it known he wishes to leave the club to make the move to Anfield.Liverpool’s interest is no secret and Craig Hope, the Mail‘s North-East correspondent, has now reported that Newcastle “are braced for a formal offer” to come “this week.”He adds that “sources on Merseyside say Diaz sale is likely to formalise Liverpool’s offer for Isak,” with Liverpool banking further funds to re-invest in their squad transformation.Liverpool previously made an approach to Newcastle to say they were prepared to discuss a fee in the region of £120 million for the Swede, with that the likely starting point.It is still maintained in some quarters that Isak is not for sale, but Newcastle are known to be in talks for Brentford‘s Yoane Wissa, with RB Leipzig’s Benjamin Sesko, Ollie Watkins and Nicolas Jackson also on their shortlist.Liverpool continue to distance themselves somewhat by simply maintaining there is “an interest” in Isak, as per the Times‘ Paul Joyce, but it is evident the club are prepared to test Newcastle‘s resolve.The Reds broke the British transfer record earlier this summer when landing Florian Wirtz in a £116 million deal, and any successful move for Isak will supersede that figure.As for Liverpool’s existing forward ranks, Diaz has been permitted to leave the club’s pre-season tour to make his Bayern move official while Darwin Nunez continues to attract interest from Saudi Arabia.