WEDDING CRASHERS star Vince Vaughn was put on the spot when he taped an appearance on American chat show The Late Show yesterday (04MAY06) - host David Letterman grilled him about his relationship with Jennifer Aniston. Vaughn and Aniston have been frequently photographed together, but have never officially confirmed they are dating. Letterman started the interview by saying, "Hey, nice going on that Jennifer Aniston thing." The couple star in upcoming film THE BREAK-UP and Letterman added that he thought they made a nice couple. An embarrassed and amused Vaughn responded, "It's very nice of you to say that, Dave, thank you. "Yeah, it's been kind of interesting for me, and I just choose not to talk about my private life that much publicly." At one point during the interview, the 36-year-old star addressed the studio audience directly saying, "Do you like the way he just kind of takes the approach that it's fact?" When Letterman then asked him to clarify the nature of the relationship, Vaughn remained firm: "I'm not saying we are or aren't a couple. "I think she's great, but I just don't discuss whether we are."