Defending champions Spain took a big step Friday towards a fourth Davis Cup final in five years when claycourt masters David Ferrer and Nicolas Almagro opened up a 2-0 semi-final lead over the United States.

Ferrer beat Sam Querrey 4-6 6-2 6-2 6-4 in the opening singles rubber on his home red clay in three hours.

Almagro then triumphed in a four-hour slog against John Isner, winning 6-4 4-6 6-4 3-6 7-5.

The 206 centimetre American’s exhaustion finally showing as Almagro peppered him with sharply-angled returns.

If Spain’s doubles team of Marcel Granollers and Marc Lopez beat the American twins Bob and Mike Bryan on Saturday, the five-time champions will be through to the final to defend their title.

In Friday’s first rubber, Querrey won the first set but the world number five Ferrer held his nerve, neutralising the gangly American’s blistering forehand with deft returns to the delight of the rowdy crowd in Gijon.

“It was a hard match, difficult at every moment,” said Ferrer, 30, currently Spanish number one in the absence of injured Rafael Nadal.

“Querrey played a very good match but in the end I was up to it.”

Ferrer broke Querrey’s serve in the first game of the match but then flagged as the American recovered to break him twice and win the set.

“I’m a bit tired, but that’s normal. It’s almost the end of the year and it’s impossible to play perfect tennis,” said Ferrer, who had arrived in Gijon straight from the US Open where he lost to Novak Djokovic in the semi-finals.

Ferrer, one of the world’s finest clay-court players along with world number 12 Almagro, soon found his rhythm and cruised through the next two sets.

He finally stamped out Querrey’s resistance in the fiercely-fought fourth, defending several break points in a series of dazzling rallies.

“David is tough, he makes you work for every point. I could have been a little more aggressive on some of the points,” Querrey said. “I think it was just a few points that were really the difference.”

Spain have dominated the Davis Cup over the past decade, winning it five times, and are surfing a wave of 23 consecutive home victories.

In the other semi-final, Argentina continued their campaign for a first-ever Davis Cup title, hosting the Czech Republic in Buenos Aires.

Juan Martin del Potro got Argentina off to a winning start with victory in straight sets against Radek Stepanek.

Del Potro, ranked eighth in the world, needed two hours and 41 minutes to beat Stepanek 6-4, 6-4, 6-2 on the clay at Parque Roca in Buenos Aires.

Juan Monaco was due to meet US Open semi-finalist Tomas Berdych in the second singles rubber later on Friday.