(Reuters) -Davis Cup heavyweights Australia and the United States eased through the first qualifying round on Saturday but Britain were knocked out as Japan hit back from 2-1 down to win 3-2, while Denmark staged a dramatic comeback to overcome Serbia.

Jacob Fearnley and Billy Harris both lost their singles matches on Saturday as Japan earned a 3-2 Davis Cup win over Great Britain in Miki, Japan to send Leon Smith's team to a relegation playoff.

Great Britain will face a relegation play-off in the Davis Cup after their makeshift team failed to make the cut and were beaten 3-2 by Japan. While Jacob Fearnley gave the side hope, this was quickly extinguished as a poor end to Saturday saw them slump out.

Japan fought back from 2-1 down to beat Britain 3-2 in their Davis Cup qualifier on Saturday to advance to the second round while the United States sealed a 4-0 victory over Taiwan. With the score tied at 1-1 after Friday's singles rubbers,