WASHINGTON - US President Barack Obama will unveil his proposals to curb gun violence at the White House on Wednesday, his spokesman said. “Tomorrow, the president and the vice president will hold an event here at the White House to unveil a package of concrete proposals to reduce gun violence and prevent future tragedies like the one in Newtown, Connecticut,” White House spokesman Jay Carney said. Obama will be joined at the event at 1645 GMT by children who wrote letters to him in the wake of the massacre of 20 young school children and six adults at the school, on December 14.