The Olympic champions, featuring Aaliyah Brown,
Allyson Felix, Morolake Akinosun and Ariana Washington, won the
opening heat in a time of 41.84 seconds, challenged only by the
British quartet who came second in 41.93.
The third automatic qualifiers were Switzerland, who ran a
national record time of 42.50, pointing to a high caliber final
later on Saturday.
Jamaica, the defending champions, were missing seven-times world
championship gold medalist Shelly-Ann Fraser-Pryce, but still
qualified second fastest in the final heat ahead of Brazil.
Germany won the second heat in 42.34.
Completing the final lineup were the Netherlands, featuring
twice 200m champion Dafne Schippers, and 2015 bronze medalists
Trinidad and Tobago.
(Reporting by Christian Radnedge; Editing by Toby Davis)
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