Manchester United have slapped a stunning €100m (£88.2m, $123m) price tag on David De Gea to ward off a potential fresh approach from Real Madrid, according to Marca.

De Gea, 27, was on the verge of completing a £29m move [BBC] to the Santiago Bernabeu in the summer of 2015 in a deal that would have seen Keylor Navas move in the opposite direction to Old Trafford as a makeweight.

However, both transfers collapsed on deadline day after paperwork failed to arrive at La Liga headquarters on time and days later the Spaniard decided to sign a new deal at United.

Yet, speculation linking De Gea with a move to Real Madrid have been constant in successive transfer windows [M.E.N].

Indeed in July, manager Jose Mourinho suggested last summer United were open to negotiating his sale but Zinedine Zidane decided to stick with Navas after the Costa Rica international helped Real to win both the La Liga and the Champions League title.

"I can guarantee that he's not going this season, that I can, and my feeling is it will be very difficult for him to go [in the future]. Because he's a very honest boy, very straight. He was contacted for a long time [by Real], the club was close, then we open [negotiations] because I always have this feeling of when a player has a desire to go I don't like to stop players to go because in the end you don't get what you expect from them if they want to move and they don't," the United boss said in July as quoted The Telegraph.

"So we open it and then they decided to close and I don't think the feeling from him [towards Real] is very, very good. I see him very happy and focused and working better than ever so for me 100 per cent he stays with us."

But speculation linking Real with a new keeper has re-emerged since Los Blancos failed to complete the signing of Kepa Arrizabalaga from Athletic Club Bilbao during the January transfer window.

Marca says that Real are yet to make a final decision on whether to sign a new number one in the summer but Los Blancos are monitoring the situation of De Gea, Chelsea's Thibaut Courtois and AS Roma's Alisson Becker in case they decide to bolster the position ahead of next season.

The Spanish publication says that the arrival of the United keeper looks now more complicated with United having increased their demands by putting a new €100m price tag on his head.

Marca points out that United are trying to tie De Gea down to a long-term deal after on Wednesday (21 February) the Spaniard proved proved his worth during the goaless draw against Sevilla in the first leg of the Champions League last 16.

De Gea's current contract expires in 2019 and United have an option to extend it until 2020 but Marca says that Red Devils would like to increase it even further.

The Times adds that the Spaniard is likely to commit his long-term future to Old Trafford with talks over a new deal worth in excess of £220,000-a-week having progressed well.