* Djokovic to play American Sam Querrey in third round
* Former world number one Ivanovic falls in straight sets (Recasts with later matches, quotes and details)
By Larry Fine
NEW YORK, Aug 28 (Reuters) - World number ones Novak Djokovic and Serena Williams sailed through brisk winds to dismiss overmatched opponents on Thursday and land comfortably in the third round of the U.S. Open.
Gusty breezes led Williams to misfire for three double faults in her first service game before the two-time defending champion found her bearings to cruise by fellow American Vania King 6-1 6-0 in 56 minutes.
"It's so hard to play in the wind," said the top-seeded Williams, seeking her sixth U.S. Open title and 18th career grand slam singles crown. "I'm very happy to get through a solid match with the conditions today.
"You have to be able to adjust," added Williams, who powered through 25 winners to just five for King.
Wimbledon champion Djokovic followed Williams onto the Arthur Ashe Stadium court and was equally efficient, gliding past French veteran Paul-Henri Mathieu 6-1 6-3 6-0.
Djokovic sounded the same note as Williams after advancing.
"It was very windy but I was able to adjust. I used my serve efficiently, getting them in," said the Serb, who pounded in 75 percent of his first serves including 13 aces without a double fault.
Djokovic joked about how his coach, Boris Becker, whose big serve in his playing days brought him the nickname "Boom Boom," would not be impressed.
"Thirteen aces he used to make in one set," joked Djokovic. "It's not a big number for him, but big for me. Glad it was working."
Most other leading seeds also stayed on course at the year's last grand slam.
Ninth seed Jo-Wilfried Tsonga of France breezed by Aleksandr Nedovyesov of Kazakhstan 6-3 6-4 6-4 and big-serving American John Isner, the 13th seed, beat German Jan-Lennard Struff in straight sets.
Tenth seed Kei Nishikori of Japan had a shorter trip through the second round as he advanced after Spain's Pablo Andujar retired while trailing 6-4 6-1.
Philipp Kohlschreiber, the 22nd seed, had an even quicker time booking a place in the third round as France's Michael Llodra retired after dropping the first set 6-2, due to an ailing elbow.
Those retirements raised the number of withdrawals in the men's draw to eight not yet halfway through the second round.
Hard-hitting American Sam Querrey limited his time spent on court against a healthy Guillermo Garcia-Lopez with his racket, beating the 28th-seeded Spaniard 6-3 6-4 6-4.
"If I keep playing like I played today I will keep going in the right direction and hopefully get back up in the top 20," said Querrey, who has slipped to 57th in the rankings.
Querrey won the dubious prize of facing Djokovic in the next round.
"Sam is one of the top Americans," noted Djokovic. "He has a big serve on any surface. If he serves well, he is dangerous."
A former world number one failed to survive the second round as error-prone eighth seed Ana Ivanovic of Serbia was ousted by 42nd ranked Karolina Pliskova of the Czech Republic 7-5 6-4.
Ivanovic, never looking comfortable against the punishing, flat groundstrokes and medley of serves launched by the 22-year-old Pliskova, committed 29 unforced errors and seven double faults.
"I really struggled to find my rhythm and made way too many unforced errors," lamented the 26-year-old Serb. "It was just really a bad day."
Also shown the door was 2011 champion Sam Stosur of Australia, who lost a third-set tiebreaker 10-8 to Kaia Kanepi of Estonia.
Wimbledon champion Petra Kvitova, the third seed, took her expected place in the third round with a 6-4 6-2 victory over fellow Czech Petra Cetkovska.
Eleventh seed Flavia Pennetta of Italy and 16th-seeded Victoria Azarenka of Belarus also advanced - both at the expense of American opponents.
Pennetta dismissed Shelby Rogers 6-4 6-3, while two-time Australian Open winner Azarenka roared back from a 3-love, 0-40 deficit at the start to beat Christina McHale 6-3 6-2.
(Editing by Frank Pingue)