U.S. President Barack Obama on Thursday made official his endorsement of Democratic presidential candidate Hillary Clinton, saying she is "so qualified" to succeed him.

"I know how hard this job can be. That's why I know Hillary will be so good at it. In fact, I don't think there's ever been someone so qualified to hold this office," Obama said in a video message.

Obama said Clinton has "the courage, the compassion and the heart to get the job done."

"I'm with her, I am fired up, and I can't wait to get out there and campaign for Hillary," he said.

Earlier this week, Clinton reached the "magic number" of delegates to win the Democratic ticket and become the first female presidential nominee of a major U.S. party.

In the November election, she will be pitted against Republican presidential candidate Donald Trump. (Yonhap)