Horsfield has scored 126 goals during his 11-year career.
Geoff Horsfield will continue to train with Lincoln City as he looks to get back into football following treatment for testicular cancer.
Horsfield, 35, spent last week with the Imps and manager Peter Jackson says he wants more time to assess his fitness.
Jackson told the club website: "It's clear he's still keen and enthusiastic.
"Everyone knows I'm looking for a striker and there's no bigger, better and stronger striker available on a free transfer than Geoff Horsfield."
The former Birmingham, West Bromwich Albion and Fulham striker had feared he would have to call an end to his playing career after being diagnosed with cancer in October.
Horsfield was given the medical all clear in after undergoing surgery.
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