Philadelphia, Jul 28 (IANS): "There has never been a man or a woman, not me, not Bill (Clinton), more qualified to be president", declared US President Barack Obama while endorsing Hillary Clinton for the Democratic Party's presidential nomination on Wednesday night.

Making a surprise appearance at the ongoing Democratic National Convention here, Obama praised his one-time rival, Clinton, whom he defeated eight years ago, as the candidate who could accomplish all that needs yet to be done.

He proudly listed his achievements and said more was needed to be accomplished and Hillary Clinton was the leader to do it.

"Our country is stronger, more prosperous than when we started," he said and ridiculed Republican presidential nominee Donald Trump's assertions that the US was a failing "crime scene".

He also praised former presidential hopeful Bernie Sanders for his efforts to end the role of money in politics and to promote a progressive agenda.

Clinton has been caricatured by both the right and the left, he said.

"She has been accused of everything you can imagine, and some things you cannot," he said.

He acknowledged that the former secretary of state had made mistakes, but asked who has not?

His portrait of Clinton was a tough, focused leader, who also was compassionate. He called her "a mother and grandmother who would do everything to see our children succeed."