Espanyol have demanded Tottenham Hotspur pay £4m to make Pau Lopez's loan move permanent ahead of the 2017-2018 campaign, IBTimes UK sources understand. However, the deal is currently far off as Spurs are only offering half of that fee - and look reluctant to match the demands of the La Liga side.

Lopez, 22, moved to White Hart Larne during the last summer transfer window after Tottenham agreed to pay around £500,000 for getting him on loan during the 2016-17 season, with an option to make the move permanent for £6.1m at the end of the campaign.

But Spurs are trying to get a cut-price deal as the Under 21 Spanish international only has 12 months remaining in his contract at Espanyol.

Tottenham have already had their first £2m offer rejected, as IBTimes UK understands that the La Liga side are demanding at least double to part ways with the keeper.

Spurs would be open to give the Catalans a percentage share of any future sale but don't plan to increase their bid as they know that they will be able to sign him as a free-agent at the end of next season.

Espanyol, meanwhile, are considering to keep Pau in their ranks to serve as a backup for Diego Lopez as current number two Roberto Jimenez is expected to move to Malaga during the coming summer transfer window.

Yet in this case, Pau will be able to negotiate a free-transfer to Tottenham from January 2018 unless the Catalas tie him to a new deal.

Lopez has failed to play a single game for the Tottenham first-team during his loan spell due to the presence of Hugo Lloris and Michel Vorm.

However, Mauricio Pochettino is still keen on making his services permanent. The Argentine boss knows him well since their early days together at Espanyol, and he sees the Spaniard as the Tottenham number one in the long-term.

Indeed, the Argentinian turned down an approach from Osasuna to lure him back to La Liga during the January transfer window because he wanted Pau to continue his development under goalkeeping coach Toni Jimenez at the Tottenham training ground.

Lloris and Vorm are already 30 and 33-years-old respectively, while Lopez is a gamble for the future.

Pau is considered one of the most promising keepers to emerge from the Spanish academy, which in recent years has overseen the emergence of top stars such as Real Madrid legend Iker Casillas and Manchester United ace David De Gea.

Nevertheless, the Espanyol academy starlet has been included in the Spanish under 21 squad for the coming Euro Championship in Poland despite his lack of playing time for Tottenham first-team during the season.