US race relations improved, but work to be done: Obama

President Barack Obama said in a commencement speech on Saturday that US race relations have improved over the last three decades, but that significant work still needs to be done.

"I tell you this not to lull you into complacency, but to spur you into action because there's still so much work to do," Obama told about 2,300 Howard University graduates in Washington, acknowledging that racism and inequality still persist. "We cannot sleepwalk through life," he said.

The United States has faced a number of racial controversies in recent years, including the 2014 shooting of an unarmed black teenager by a police officer in Ferguson, Missouri, that sparked sometimes violent protests.