Varney has attracted a host of admirers including Middlesbrough, Derby, Leicester and local rivals Stoke after scoring 25 goals for Alex this season.
However, Addicks boss Alan Pardew is the first to make a firm bid and the 24-year-old is expected to complete a move to The Valley later this week.
Varney's arrival is almost certain to lead to the departure of Darren Bent, who has been linked with a number of top Premiership clubs including Liverpool, Tottenham, West Ham and Newcastle.
Meanwhile, Iwelumo is expected to be unveiled as a Charlton player on Monday after agreeing a deal to reunite with his former Us boss Phil Parkinson.
Parkinson is now assistant manager at The Valley and has long been an admirer of the giant forward, first signing him from German side Alemania Aachen in 2005.
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