Humbert’s victory gave France an unassailable lead after Adrian Mannarino defeated Dominic Stricker 3-6, 6-1, 6-4 in Group B play.
The doubles pairing of Nicolas Mahut and Edouard Roger-Vasselin sealed the 3-0 French victory by beating Marc-Andrea Huesler and Wawrinka 6-2, 6-2.
Australia and Britain square off in Group B on Wednesday in Manchester.
Laslo Djere and Dusan Lajovic won singles matches in Serbia’s 3-0 victory over South Korea in Group C at Valencia — with Spain and the Czech Republic next playing in the Spanish city.
In Group A, Chile defeated Sweden 3-0 behind singles victories by Cristian Garin and Nicolas Jarry. Defending champion Canada and Italy are also in the group.
The Netherlands won 2-1 over Finland in Group D, where Croatia will face the United States.
The top two countries in each group advance to the Final 8 in November at Malaga.
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