Obama honors Martin Luther King Jr with school project WASHINGTON (Reuters) - President Barack Obama on Monday paid tribute to slain civil rights leader Martin Luther King Jr. by helping build a library reading nook at a local school, saying service and diversity make America the "strongest, most extraordinary country on earth." The president, first lady Michelle Obama and their daughter Malia marked King's birthday by helping spruce up the library at Browne Education Campus, named after 19th-century African-American rights advocate Hugh M. Browne. It serves elementary and junior high school students in a predominantly African-American community in northeast Washington. Next to it is the historic Langston Legacy Golf Course, a formerly segregated course for African-American golfers. Speaking underneath a sign reading "United we serve," Obama praised the nation's diversity. "At a time when the country has been going through some difficult economic times, for us to be able to come together as a community, people from all different walks of life, and make sure that we're giving back, that's ultimately what makes us the strongest, most extraordinary country on earth," he said. Obama, who is up for reelection in November, has been criticized by some Republican opponents as not believing in American exceptionalism, the idea that the United States and its values are unique and worthy of imitation. The Obamas greeted adults and children at the school, then headed to its library where they built book shelves and set out bean bags and sitting mats on the floor. Balancing on a step-ladder, Obama painted words onto the wall: "The time is always right to do what is right," a quotation by King. Obama said it was the third time his family had celebrated King's birthday with a community service project. Editing by Ellen Wulfhorst