Sanchez has won 88 caps for Colombia and played in the Premier League for Aston Villa between 2014 and 2016.
The new season is right around the corner and, inevitably, that means changes to the schedule will occur for every Premier League side - and West Ham have today learned that two of their fixtures in October and November have been moved for TV coverage.
It has been a really busy summer in east London and the 29-year-old Perez becomes West Ham's eighth new signing, as manager Manuel Pellegrini overhauls his squad.More news: Republicans Only Force Stopping Trump Impeachment, Nunes Says
Meanwhile, NAIJ.com had earlier reported that West Ham United have confirmed the signing of Lazio attacking midfielder Felipe Anderson for a club-record fee of a £40m.
The former Rayo Vallecano forward paid tribute to the Arsenal supporters in a message on his Twitter account, saying: "They always showed me affection and love from the first time I arrived in London".
"In Spain there are also interest from some clubs, but they are not willing to assume the transfer".