Sporting CP are waiting for Manchester United to make an offer for midfielder Bruno Fernandes before they decide whether to accept Tottenham Hotspur's proposal.
Spurs recently met with Fernandes' agent to try and negotiate a deal, and it was thought that United may be forced to leap into action to avoid losing him to a Premier League rival.
Ole Gunnar Solskjaer is eager to push through a deal as soon as possible, so the Red Devils are expected to come in with a formal offer in the near future.
The Portuguese side are demanding around £70m for Fernandes, although most involved in the situation are said to believe that that is nothing more than a negotiating tool, with a fee of £45m thought to be more realistic.
Midfield reinforcements are thought to be high on Solskjaer's list of priorities this summer. Alongside Fernandes, a deal for Newcastle United youngster Sean Longstaff has also been suggested, but their recruitment is likely to depend on the future of Paul Pogba.
The Frenchman is thought to be a target for both Real Madrid and Juventus, after admitting his desire to leave Old Trafford in search of a "new challenge". United insist that he is not for sale, although they may be forced to change their stance as the summer progresses.
The plan is to pursue both Fernandes and Longstaff, regardless of what happens with Pogba, although they may be forced to act sooner if Pogba does show any signs of wanting to leave.
Fernandes, who racked up 32 goals and 18 assists for Sporting CP last season, is widely viewed as one of the hottest properties in Europe, with plenty of European giants thought to be keen.
However, United and Spurs are thought to be leading the way, and negotiations may be lengthy if Sporting try and stick to their £70m asking price.