NEW YORK (REUTERS) - Rain delayed the start of play on the outer courts of the US Open on Wednesday (Aug 28), but the second-round clash between seventh seed Kei Nishikori and Bradley Klahn began as scheduled under Louis Armstrong Stadium's closed roof.

Nishikori and Klahn will be followed by fifth seed Elina Svitolina taking on Venus Williams on Armstrong, which opened last year following a five-year, US$600 million (S$830 million) renovation project at the Billie Jean King National Tennis Centre.

Big-hitting American Madison Keys will take on China's Lin Zhu in the final day session match on Armstrong.

The wet weather is not expected to impact the schedule on Arthur Ashe Stadium, which also has a retractable roof.

Third seed Karolina Pliskova was set to kick off the day session against Georgian qualifier Mariam Bolkvadze before third seed and five times champion Roger Federer closes out the day session when he takes on Damir Dzumhur.

After brutally hot conditions at the tournament last year, this year's US Open has been marked by cooler weather but rain is forecast to continue on Wednesday evening.