DALLAS - President Barack Obama says the shootings of five Dallas police officers would appear to have exposed the "the deepest fault line of our democracy" but that Americans must reject such despair.

Obama spoke Tuesday at the memorial service for the five, honoring the work of law enforcement officers, saying they answer a call that at any moment, even in the briefest of interactions, may put their life in harm's way.

He said fewer people are being mourned at the service because of the brave actions of the officers killed.

Obama attended the memorial along with first lady Michelle Obama, Vice President Joe Biden and his wife, Jill Biden.

The five who died were shot during a protest against the police killings of black men in Louisiana and Minnesota. Nine officers and two civilians were injured in the attack.