Donald Trump joins fray

Property tycoon Donald Trump, one of America's most flamboyant and outspoken billionaires, threw his hat into the 2016 race Tuesday for the White House, promising to make America great again.

The 69-year-old long-shot candidate ridiculed the country's current crop of politicians as "stupid" and vowed to take on the growing might of China in a speech launching his run for the presidency.

"I am officially running for president of the United States and we are going to make our country great again," he said from a podium bedecked in US flags at Trump Tower on New York's Fifth Avenue.

Trump identifies as a Republican and has supported Republican candidates in the past. But in his speech he did not explicitly say if he was running for the party's nomination or as an independent.

He trails in polls behind rival Republican candidates. Last month, just five percent of voters said would vote for Trump at the Republican primary, according to the Quinnipiac University.

And in March, 51 percent of all voters said they would definitely not vote for him, another Quinnipiac poll found.