World number three Rafael Nadal was given a stern test by Nicolas Kiefer before coming through in four sets to reach round three of the US Open.

The Spaniard dominated the first set but a number of unforced errors allowed the veteran back in before he regained control to win 6-0 3-6 6-3 6-4.

The 23-year-old will next face 32nd seed and compatriot Nicolas Almagro.

Elsewhere, sixth seed Juan Martin Del Potro and seventh seed Jo-Wilfred Tsonga eased through in straight sets.

World number two Andy Murray recovered from a second-set blip with some superb tennis to brush aside Paul Capdeville and reach round three of the US Open.

The 22-year-old looked on course for a routine win when he eased through the first set but an inspired Capdeville stunned the Scot by taking the second.

Murray responded with some of his best tennis, though, firing 44 winners on his way to a 6-2 3-6 6-0 6-2 victory.

In a monumental four-hour five-setter, American wildcard Taylor Dent set up a third round clash with Murray after beating Spain's Ivan Navarro in a five-set epic.

Ranked 195th in the world and playing in his first US Open since 2005 after a long-term back problem, Dent won the first set but then had to fight back after losing the next two.

The 28-year-old won the decider 11-9 on a tie-break and afterwards grabbed the umpire's microphone and thanked the crowd.

"The crowd just never stopped," Dent said. "They never stopped kind of being my third leg out on the court. They were just with me the whole time.

"When I started to turn it around, I mean, the emotions just boil over here. The US Open is such a unique experience for a tennis player. It's really unbelievable that I have the privilege to experience it."

Nadal, still finding his form after a two-month break with knee problems, produced a patchy performance against Kiefer, who had previously failed to take a single set off the Spaniard in four career meetings.

The six-time Grand Slam champion stormed to the first set, but the 32-year-old German hit back to level the match with a devastating combination of drop shots and defensive play to stun his opponent.

The third set was a more steady affair, going with serve until Nadal edged a thrilling eighth game to send the Spaniard into full fist-pumping mode.

After getting within one set of victory, the spring seemed to return to Nadal's step and he did not have to wait too long before securing a highly entertaining victory.

"I feel good," Nadal said. "I started playing well but I think he started slow and later played better.

"It's difficult like that because you are not on rhythm. Nicolas is a very difficult player and I'm very glad to beat him."

It was a fairly comfortable passage for Argentina's Del Potro over Jurgen Melzer in three sets, winning 7-6 (8-6) 6-3 6-3.

The semi-finalist at this year's French Open will next face Daniel Koellerer for a place in the fourth round after the Austrian overcame an early test from Uruguayan Pablo Cuevas to win through 3-6 6-2 6-1 6-4.

France's Tsonga was in dominant mood as he conquered Finland's Jarko Nieminen 7-5 6-3 6-4 with the help of 45 winners to reach the third round for the third successive year.

The 24-year-old, who has never reached the fourth round at Flushing Meadows, next faces compatriot Julien Benneteau after he claimed a surprise 6-1 3-6 6-1 6-0 victory over 30th seed Viktor Troicki.

Benneteau was near indomitable on his first serve, winning 67% of the points, and he forced seven breaks of serve as Troicki struggled to click into gear.

Meanwhile, Marin Cilic, who endured 50 unforced errors, had to dig deep to beat Jesse Levine 4-6 2-6 6-0 6-3 6-0.

Cilic served 14 aces and enjoyed a win percentage of 75 on his first serve to help him into the third round and a match-up with Uzbekistan's Denis Istomin, who beat Nicolas Lapentti 2-6 6-4 4-6 7-5 7-6 (7/4).

Another seed who had to battle back from a 2-0 deficit was Spain's former world number one Juan Carlos Ferrero.

The 24th seed looked in dire straits early on in his match against German Philipp Petzschner, but regained his composure and used all of his Grand Slam experience to edge through 1-6 3-6 6-4 6-2 6-4.

Next up for Ferrero is Gilles Simon, seeded ninth, who produced an efficient display to dispatch Brazilian Thomaz Bellucci 6-3 6-2 6-4.

Another Frenchman Gael Monfils, seeded 13th, also went through when he beat Germany's Andreas Beck 6-3 7-5 6-3 and plays Argentine Jose Acasuso next after the world number 47 upset 18th seed David Ferrer of Spain 6-3 3-6 1-6 6-3 6-2.

Number 17 seed Tomas Berdych will play Fernando Gonzalez - a 6-4 6-7 (5-7) 6-3 6-4 winner against Josselin Ouanna - after overcoming Horacio Zeballos 6-3 6-7 (3-7) 7-6 (7-2) 6-2.

From BBC Sport