The Magpies have already seen two bids rejected by Watford for the highly-rated central defender.
Pardew is keen to bolster his defensive options before the close of the transfer window as he seeks to bring in cover for the injured Steven Taylor.
Watford are reluctant to lose Mariappa with the 25-year-old a key member of Sean Dyche's side and they are thought to have rejected an offer from Wigan for the player.
Pardew has now left the ball in Watford's court saying Newcastle will not improve their latest offer for Mariappa.
"We have made our last bid now and it's a final bid so if he doesn't come today then he probably won't come to this football club because in the summer we will probably look elsewhere," said Pardew.