Manchester United are facing a tough battle to prise Renato Sanches from Benfica this summer because the Portuguese champions are eager to keep the gifted teenage midfielder for another season.

Sanches, 18, a fast, powerful box-to-box midfielder, has been a revelation since breaking into the Benfica first team last October and is widely regarded in Portugal as the most exciting talent to emerge in the country since Cristiano Ronaldo.

United have had Sanches watched extensively in recent months and were due to dispatch a scout to run the rule over him playing the player for Portugal in their friendly against Belgium in Leiria on Tuesday night.

Benfica’s strong preference is to retain Sanches’ services for another 12 months in the belief that his valuation is likely only to increase although such a stance would also work as a strong negotiating tactic given the clamour among Europe’s leading clubs for him.

Real Madrid, Bayern Munich and Barcelona are also among those interested but Benfica are thought to want at least €60 million (£47 million) with a substantial upfront payment in the region of £30 million.

United are mindful that the projected £61.6 million fee they paid Monaco last August for Anthony Martial, then a 19-year-old forward who was relatively unknown outside his native France, has raised the price for Europe’s most talented youngsters, just as the Premier League’s impending new £8 billion television deal is forcing up fees for English clubs.