Mainz, however, are confident that they can command a fee upwards of £35m for Mateta's services, and as such are likely to reject the Magpies bid.
The report goes onto claim that Southampton are among a number of other unnamed sides who have made a bid for Mateta, though it's unclear whether the offers match Mainz's lofty valuation.
Prior to his Germany move, Mateta struggled to break into the first team picture at Lyon, despite enjoying a fine goalscoring season on loan at Ligue 2 outfit Le Havre during the 2017/18 campaign.
Mateta netted 20 goals in 38 appearances in all competitions, persuading Mainz to part with £9m in order to bring him to the Bundesliga. He has impressed again this season, with his impressive goal tally helping Die Nullfünfer finish comfortably in mid-table.
Newcastle's alleged pursuit of Mateta is likely to be complicated by the ongoing takeover rumours surrounding the club, as owner Mike Ashley continues talks with Sheikh Khaled bin Zayed Al Nehayan over a potential sale.