India thus ended the tournament with a bronze medal, equalling the performance of 2009 (Vijender Singh), 2011 (Vikas Krishan) and 2015 (Shiva Thapa).
Despite the loss, the 24-year-old from Delhi joined a rare club of world championship medallists from India -- the past winners being Vijender, Vikas and Shiva.
In a bout fought primarily on defensive tactics, the 20- year-old American had the slight edge in the opening three minutes. Although both the boxers spent the better part of it waiting for the other to make the first attack, the grunting Ragan seemed more in control lunging forward.
The second round was fought on a more even keel and Gaurav managed to surprise his rival by cornering him on more than one occasion.
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Both the boxers went on the defensive in the final round but Ragan broke free with his cleanly-struck right hooks to clinch the issue.
Ragan will now face England's Peter McGrail in the final on Saturday.
Earlier, Amit Phangal (49kg) and Kavinder Bisht (56kg) had bowed out in the quarterfinal stage.
Ousted in the Asian Championships quarterfinal stage, Gaurav had also gone on to lose the box-off for a world championship spot.
It was a stroke of good luck that he ended up being handed the wildcard that was originally meant for Bhutan. The Asian Boxing Confederation (ASBC) gave the lucky entry to Gaurav after Bhutan declined the offer.
However, he made the lucky break count by upstaging Ukraine's Mykola Butsenko in the prequarterfinal. Butsenko is a two-time European Championships' silver-medallist and the 2013 world championships' bronze-winner.
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