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Orlando Bloom's admitting he and Katy Perry have a tough time keeping the romance going in their relationship -- but it definitely isn't for lack of physical beauty, which is crystal clear in some new photos.

Kurt Iswarienko/Flaunt Magazine

Orlando's leaving very little to the imagination ... showing off his abs and more, appropriately, for the new issue of Flaunt. Once you get past the images -- if you can -- he also spoke to the magazine about his fiancée Katy.

Far from gushing about their relationship, Orlando said, "Sometimes things are really, really, really, challenging. I won’t lie. We definitely battle with our emotions and creativity."

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