Spain reached their sixth Davis Cup final in 10 years after David Ferrer gave them an unassailable 3-1 semi-final lead over the United States by beating John Isner 6-7 (3/7), 6-3, 6-4, 6-2 on Sunday.
Spain will travel to either Argentina or the Czech Republic for the final, depending on which of those countries prevails in the other semi-final due to be decided later on Sunday in Buenos Aires.
The United States had kept the tie alive with the five-times champions with a doubles victory by the twins Bob and Mike Bryan on Saturday, but US Open semi-finalist Ferrer on his favourite red clay prevailed over Isner, the world number 10.
The six-foot, nine-inch American beat Ferrer in a tie-break in the first set but the Spaniard dominated the following three.
Ferrer, currently number one in his country in the absence of the injured Rafael Nadal, tamed Isner's formidable serve and aggressive style with precision returns and passing shots and capitalised on a series of unforced errors.
It was the 16th Davis Cup victory in a row for Ferrer on clay.
Nadal could make a return for the final in November if he recovers from the knee injury that kept him out of the Olympics and the US Open this summer.
The United States - the most successful team overall in Davis Cup history with 32 victories - admitted they were not favourites when they came to Spain for the tie.
But under the captaincy of former Grand Slam-winner Jim Courier, they have chalked up back-to-back away wins in Switzerland (5-0), where Isner shocked Roger Federer, and France (3-2), where he defeated Jo-Wilfried Tsonga.
Spain have dominated the Davis Cup over the past decade, winning it five times, and are surfing a wave of 23 consecutive home victories.
Argentina's hopes of making the final suffered a double blow on Saturday when they slipped 2-1 down to the Czech Republic in the semi-finals and lost top player Juan Martin Del Potro through injury.
Spain beat Argentina in the final in 2008 and 2011. The fifth match of the Spain-USA tie in Gijon, due to be played between Nicolas Almagro and Sam Querrey, was called off after Ferrer's victory determined the tie.