President Obama wrapped up his media blitz Monday night with an appearance on Late Show With David Letterman. The president had an irreverent answer for Letterman when he asked if the virulence of the health-care debate was fueled in part by his race. "First of all, I think it's important to realize that I was actually black before the election," Obama said, provoking big laughs from the audience. Letterman quipped: "How long have you been a black man?" The 40-minute interview tackled mostly serious topics. Obama said he has not yet decided whether to send more troops to Afghanistan, and addressed the sobering unemployment numbers, calling it a "big problem" for at least another year. The president starts participating in the United Nations General Assembly in New York this week.