(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.

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.

The United States beat Taiwan 4-0 in Saturday's Davis Cup qualifiers in Taipei City behind the experience of Olympic silver medalists Austin Krajicek and Rajeev Ram.

Alex Michelsen gave the United States a 2-0 lead over Taiwan on his Davis Cup debut in the first round qualifiers on Friday, while Jacob Fearnley also impressed in his first appearance in the competition to pull Britain level with Japan.

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.