Sources: Stoke City boosts offer for Harrison but NYCFC still holding out for more

Jack Harrison is still a New York City FC player, but Stoke City is doing everything it can to change that before the January transfer window closes.

The Potters have increased their bid for the 21-year-old English winger significantly from the $4.5 million offer first reported by Goal on Saturday. Multiple sources tell Goal that Stoke City has made a $7 million offer, with one source saying Stoke's bid could push up to $10 million with incentives.

The considerable increase comes amid reports of interest from other teams in the Premier League, including West Ham and Leicester City. If Harrison's eventual transfer does reach the $10 million mark, it would equal Jozy Altidore's 2008 transfer to Villarreal as the largest fee ever paid for a MLS player.

Though the sides have continued negotiations through this week, sources tell Goal a deal has not come close to being finalized yet, with NYCFC eager to secure as large a fee as possible, in part because the club is only due to receive 50 percent of any transfer, with the other 50 percent going to MLS. That percentage would go up to 75 percent for NYCFC after the 2018 season, which has Patrick Vieira's club pushing for a bigger payout.

Even at $7 million, the fee would break the MLS record for a fee paid for a player born outside of the United States, surpassing past sales of Stern John and Jermain Defoe.

Harrison, who was born in Stoke before moving to the Bolton area and spending seven seasons in Manchester United's youth setup, would be the first player sold to a top European league by NYCFC in its brief history.

The 21-year-old attacker is coming off an impressive second season as a professional, having recorded 10 goals and six assists, and playing well enough to earn a call-up to the England Under-21 national team last fall.

Stoke City is currently locked in a relegation fight, having recently appointed Paul Lambert as its new manager. The Potters climbed out of the relegation zone after Saturday's 2-0 win against Huddersfield Town.