Trump considering pardon for Jack Johnson

US President Donald Trump says he is considering "a Full Pardon!" for boxing's first black heavyweight champion more than 100 years after Jack Johnson was convicted by an all-white jury of "immorality" for one of his relationships.

Trump tweets that the actor Sylvester Stallone called him to share Johnson's story.

Johnson won the world heavyweight crown in 1908 in Sydney, beating the reigning Tommy Burns of Canada. The fight is still considered to be among the biggest ever staged in Australia and drew 20,000 people to the old Sydney Stadium at Rushcutters Bay.

Trump says Johnson's "trials and tribulations were great, his life complex and controversial."

"Others have looked at this over the years, most thought it would be done," the president wrote, "but yes, I am considering a Full Pardon!"

Johnson was convicted in 1913 for violating the Mann Act, which made it illegal to transport women across state lines for "immoral" purposes.

The boxer, known as the Galveston Giant, died in 1946. His great-great niece has pressed Trump for a posthumous pardon.