Berdych, Wawrinka into US Open last 16
Tomas Berdych of the Czech Repubic returns a shot to Julien Benneteau of France during their 2013 US Open men's singles match on September 1, 2013 in New York.
Fifth seed Berdych, who defeated five-time winner Roger Federer on his way to the semi-finals last year, eased past French 31st seed Julien Benneteau, 6-0, 6-3, 6-2.
Swiss ninth seed Wawrinka, a quarter-finalist in 2010, got past unseeded Cypriot Marcos Baghdatis, the former world number eight but now down at 53 in the world, 6-3, 6-2, 6-7 (1/7), 7-6 (9/7).
Baghdatis, the 2006 Australian Open runner-up, has now lost all three meetings with Wawrinka.
The bearded Cypriot saved four match points before falling in a big-hitting clash on Louis Armstrong Stadium, which saw a total of 100 winners unleashed.
Berdych hit 36 winners and 11 aces in the contest, which finished six minutes short of two hours.
"It was a bit hot, a bit humid, but otherwise the tennis was good," said Berdych, who has made the quarter-finals at the Australian Open and Wimbledon this year.
"I managed to stay focused from the first point until the last. There were no ups and downs, just took all my chances that I had, and won in straight sets."
Wawrinka has a 6-5 career lead over former Wimbledon finalist Berdych, having won their last meeting on clay in the Madrid Masters semi-finals this year.
Third seed Andy Murray, who is also the Olympic and Wimbledon champion, disposed of Leonardo Mayer in the second round and will face another Mayer -- Germany's Florian Mayer -- for a place in the fourth round.
Murray has a 2-0 career lead over the 29-year-old German, winning their most recent meeting in two tiebreak sets on the Madrid clay earlier this year.
Mayer, the world number 47, has twice been a Wimbledon quarter-finalist in 2004 and 2012 but has never gotten beyond the third round in New York.
Top seed Djokovic, the 2011 champion, takes on unseeded Joao Sousa, the first Portuguese player to make the third round in New York.
Tommy Haas, the German 12th seed and at 35 the oldest man in the tournament, tackles Russia's Mikhail Youzhny.
A victory could pit Haas against Lleyton Hewitt, the 32-year-old ex-champion, in the fourth round.
The Australian stunned sixth seed and 2009 champion Juan Martin Del Potro in the second round for his first win over a top 10 player in New York since his victory over Pete Sampras in the 2001 final.