President Barack Obama said the nation was grieving for those killed during the "tragic shooting" in Newtown, Connecticut.
During his weekly radio and television address, the President said, "We have endured far too many of these tragedies in the last few years ... We have to come together and take meaningful action to prevent more tragedies like this. Regardless of the politics".
More top news
Four in 10 European doctors are considering leaving the UK following Britain's vote to leave the EU, research suggests.
Eating 10 portions of fruit and veg every day could could significantly reduce the risk of heart disease and cancer, researchers say.
North Korea has blamed Malaysia for the death of Kim Jong-nam, the half-brother of North Korean leader Kim Jong-un.