Obama endorses Clinton as 'optimistic choice' for America's future

President Barack Obama endorsed Democratic nominee Hillary Clinton as his successor, contrasting her as the optimistic choice for Americans against Republican nominee Donald Trump.

"I am more optimistic about the future of America than ever before," Obama told thousands of delegates at the Democratic National Convention, praising Clinton as uniquely qualified to succeed him.

Obama said that at the Republican convention last week that nominated Donald Trump, "there were no serious solutions to pressing problems -- just the fanning of resentment, and blame, and anger and hate."

Although the president nearly talked himself hoarse by the end of his endorsement speech, he invoked his renowned rhetorical skills before the party faithful.

In a delivery mixed with humour and his best known phrases such as "Yes we can" and "the audacity of hope", Obama announced Clinton as the most qualified person to lead the US.

That included himself and her husband, former president Bill Clinton.

"There has never been a man or a woman, not me, not Bill, nobody more qualified than Hillary Clinton to serve as president of the United States of America," Obama said.

When Obama brought up Trump he was answered with boos from the crowd.

"Don't boo, vote," he told the convention hall.

"The Donald is not really a plans guy. He's not really a facts guy either."

The president's swipe was somewhat personal with Trump being one of the most vocal leaders of the "birther" movement – those who doubted Obama was born in the US.

"He calls himself a business guy – which is true.

"But I know plenty of businessmen and women who've achieved remarkable success without leaving a trail of lawsuits and unpaid workers and people feeling like they got cheated."

Clinton herself made an appearance with the president at the end of the speech, waving to the crowds of delegates but keeping her address for the final day of the convention.