Lisbon are keen for Mendes to replace Fiorentina-bound Miguel Veloso and are will be prepared to fork out the £1.5million needed to prise the star from Ibrox.

The 30-year-old, who is recovering from knee ligament damage, is also keen on the move as it will boost his chances of winning a place in his national squad for the World Cup in South Africa.

However, Sporting director Ricardo Sa Pinto has confessed his club cannot match the £20,000-a-week pay packet the former Champions League winner is picking up in Scotland.

Sa Pinto hopes to lure Mendes back to the country of his birth with the promise of financial incentives if the club wins their domestic league this season. A club source said: “The main problem is the high salary that he receives in Glasgow, but Sporting are looking for a sponsor to help increase his wages.

“But the coach Carlos Carvalhal believes the return of Pedro is vital for the future of his team and is urging the board to do everything they can to agree a contract with the player and Rangers.”

Mendes, though, is only concentrating on getting back in action for Rangers – and is hopeful he will be back playing within the next fortnight.

The former Spurs and Portsmouth player has not featured for Walter Smith’s side since sustaining a serious injury in the 4-1 defeat by Romanian minnows Unirea Urziceni at Ibrox eight weeks ago.

He said: “I’m in the final stage of my recovery. That’s all I am thinking about.”

He added: “Sporting is a great club that fights to win titles, but it is important, to prevent any more speculation, to emphasise that they did not contact me.

“If something happens, very well. With any proposal, we would have to study it and see what would be better for me and for Rangers.”

Mendes, a £3million signing from Portsmouth last season, could struggle to win back a first team place when he returns from injury.

Lee McCulloch and Steven Davis have done well in central midfield as Rangers have gone six games unbeaten in the league. Maurice Edu is fit again and Kevin Thomson is also expected to return soon.

Mendes is keen to play regular first team football in the run-up to the World Cup in South Africa. He added: “After being involved in the past, I hope to be involved in the national squad again.”