Former US President Barack Obama in early excerpts released from his speech for the Democratic National Convention later on Wednesday (local time) said President Donald Trump has diminished the United States' proud reputation around the world.

"Donald Trump hasn't grown into the job because he can't," Obama said in the excerpt released on Wednesday. "And the consequences of that failure are severe. 170,000 Americans dead. Millions of jobs gone. Our worst impulses unleashed, our proud reputation around the world badly diminished, and our democratic institutions threatened like never before."