The 19-year-old is due to return to his parent club Udinese in July, but River are in negotiations with the Italians over an extension to his stay.

Having recovered from an ankle ligament injury, Sanchez was in fine form for the Argentinean giants in the pre-season tournament they won last month.

River official Norberto Alvarez said the club want to extend the deal until the end of the year.

He told the website of Chilean newspaper La Tercera: "Discussions with Udinese have begun to acquire Sanchez for as long as possible, but it is something that will be difficult to achieve.

"They (Udinese) want him back in July. They do not want to loan him or do anything else, but the worst negotiations are the ones you don't try."

Sanchez arrived at River at the beginning of the 2007/08 season, and has since scored two goals in six first-team games for the Argentinian outfit.