The Sun says despite initially insisting he would not make any transfer window signings, Arsenal's boss is now ready to reinforce his inconsistent defence.
Newcastle have been haggling over a price for 25-year-old Mariappa, who can play either at right-back or centre-back.
Toon chief Alan Pardew has offered £1.5million so far.
While Watford are demanding £4million, they will accept just over £2m.
Wenger had Mariappa watched in Watford's home FA Cup defeat by Tottenham last Friday.