Katie Boulter put Great Britain 1-0 ahead in their Billie Jean King Cup play-off against Mexico with a straight-set win over Marcela Zacarias.
The 24-year-old was tested early on in a 7-5 6-0 victory that gave the hosts the lead in the best-of-five tie.
Heather Watson, the top-ranked player in the tie, faces Giuliana Olmos later on Friday, while Saturday features the reverse singles and a doubles rubber.
Victory would put Great Britain one win from qualifying for the 2022 Finals.
The Billie Jean King Cup is the new name for the Fed Cup, the women's international team event that Great Britain have finished runners-up in four times but have never won.