Middlesbrough are yet to agree a transfer fee with Spanish outfit Real Mallorca for USA international striker Matthew Hoppe, sources have exclusively informed Football League World.

And the Teessiders are now concerned that other clubs could now pip them in the chase for the 21-year-old.

It was reported across the Atlantic Ocean in the past week that Boro had submitted an offer worth $3 million (£2.44 million) for Hoppe, with their North East and Championship rivals Sunderland also keen on the youngster.

Despite the six-cap international being left out of his La Liga club's squad for their pre-season friendly against Napoli at the weekend, Hoppe is seemingly no closer to becoming a Boro player as they have not yet met Mallorca's asking price.

Hoppe joined the Spaniards last summer, having scored six times in 23 league appearances for Schalke in Germany.

Boro are in the hunt for multiple new attackers even following the arrival of Marcus Forss from Brentford last week, but they could lose out for Hoppe if they do not up their bid for the American.