Paraguayan Cardozo, 29, has a buyout clause of 60 million euros, the Lisbon club said on their website.
Cardozo has netted a league leading 13 goals this season and is Benfica's top foreign scorer of all time - approaching the 150 goal mark since arriving in 2007 from Argentine club Newell's Old Boys.
Holding midfielder Nemanja Matic, one of the top performers in Benfica's 2-2 draw against Porto in Sunday's 'Classico', and Brazilian centre-back Jardel, penned new contracts on Monday. They have buyout clauses of 45 million euros and 20 million euros, respectively.
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