Sporting Kansas City fullback Fede Bessone is training with Millwall.
Bessone signed for the MLS club in September 2013 but ended up leaving without making a first-team appearance.
The Argentinian, who once had a loan spell with Charlton from Leeds, told Sky Sports: "The club (Sporting KC) offered me a new three-year deal.
"We were close. It was a difficult decision for me not to stay there, but it's great to be in London again."
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