POTUS sat down for an interview with Lester Holt, which is airing Monday -- the first look of which was played on NBC ... where the veteran news anchor peppered JB with questions about using that phrase during a donor call last Monday post-debate debacle.

If you hadn't heard, Joe was quoted as saying ... "It’s time to put Trump in the bull’s-eye." Of course, in the wake of Thomas Matthew Crooks trying to take a shot at DT ... many have been critical of Biden saying that, suggesting it may have incited the young to action.

Welp ... Joe says he regrets his language -- noting he only meant it was time to put the focus on Trump as opposed to himself, but even so ... he says he's sorry and notes he probably should've used different terminology.

In the same breath ... Joe also did a bit of whataboutism as Lester grilled him on his rhetoric -- wondering whether using over-the-top language to describe Trump and a potential second term as potentially incendiary and spurring some to take action into their own hands.

Joe defended himself and said that he's accurately trying to describe what he considers a true threat to democracy ... and noted that Trump's language/rhetoric is far worse than his.

Biden asks the rhetorical question -- what do you do when someone poses a serious threat to this country ... not talk about it honestly because it might potentially incite somebody???

It's a tough topic obviously ... and you can tell Joe's trying to walk a fine line here. You can also sense Biden is trying to turn down the temperature on all this -- but still needing to apply pressure since he's in a tight race with DT ... one that some suggest might be over now.