Great Britain will have to fight back from behind to reach the Billie Jean King Cup final after Heather Watson lost the opening rubber of the semi-final against Australia in Glasgow.
If Harriet Dart loses to Ajla Tomljanovic in the next singles rubber, Australia will secure victory.
If the Briton wins, the best-of-three tie will go to a deciding doubles.
Great Britain had played their previous two ties in the evening and the change to a morning start on Saturday seemed to affect Watson.
"I think I just didn't feel as fresh as I did then," she said.