(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.

Great Britain face a Davis Cup relegation play-off after losing their first-round tie 3-2 against Japan. With the tie level at 1-1 after Friday's opening day, Britain took the lead when Neal Skupski and Joe Salisbury won Saturday's opening rubber 7-6 7-6 against Yosuke Watanuki and Takeru Yuzuki.

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.

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.

Alex Michelsen hung on to defeat Tung-Lin Wu and help the United States take a 2-0 lead in their matchup against Taiwan in Davis Cup qualifiers on Friday in Taipei City. American Marcos Giron opened the tie with a 6-2,