* Berdych recovers to beat Monaco in five sets
* Del Potro overcomes wrist pains to crush Stepanek (Updates with Berdych win)
By Rex Gowar
BUENOS AIRES, Sept 14 (Reuters) - World number six Tomas Berdych fought back to beat Juan Monaco 6-1 4-6 1-6 6-4 6-4 in a thriller to put Czech Republic level at 1-1 with Argentina in their Davis Cup semi-final on Friday.
The Argentines, aiming to reach a second straight final and fourth since 2006, won the opening singles at Parque Roca with Juan Martin del Potro's 6-4 6-4 6-2 victory over Radek Stepanek.
An emotional Del Potro, torn between what is best for his career and his desire to play for his country, had considered pulling out of the tie because of pains in his left wrist.
Monaco recovered strongly from losing the first set with confident strokes and accuracy on his first serve while Berdych conceded unforced errors and double faults on crucial points.
During the second and third set, Berdych struggled with his length and lost many points with long drives but began putting his shots just inside the lines from midway through the fourth.
The Czech suddenly rediscovered his early consistency at 4-2 down in the fourth set, winning eight consecutive games.
Monaco went down fighting, though, breaking Berdych twice in the fifth set after falling 4-0 behind.
The Argentine handed Berdych three match points on his serve with the Czech clinching victory on the first with a winning backhand return down the line.
EMOTIONAL DEL POTRO
Earlier, tearful Del Potro could barely speak in a courtside interview after beating Stepanek to put the home team 1-0 up.
"How I suffer playing, just for you, a lot for you, I played to thank the fans for their affection, the support they give me," the Olympic bronze medallist, choking back the tears, told the crowd.
"The important thing is for me to be here... We all have pains, more or less bad... I know the one up there is looking after me," added the world number eight after the match played to a backdrop of raucous, soccer-style chanting by the crowd.
Stepanek, who had won three of their four previous meetings, said he did not see his rival struggling and suggested Del Potro's wrist problem might have been pre-match gamesmanship.
But the Argentine told a news conference his pain was real out on the clay court at the Mary Teran de Weiss stadium.
"It was very emotional playing this match. I enjoyed the moment, the decision to take a risk," the lanky 23-year-old, sensitive to weaknesses in his wrists, said.
"I think everyone could see how I played, I didn't have winners with my backhand. It's super hard to play like that but my serve helped me," said Del Potro, who seven months after winning the 2009 U.S. Open had surgery on his right wrist.
"When you can't do damage with all your shots it gets complicated. It's frustrating not being able to be aggressive on one side," added the Argentine who missed most of the 2010 season because of the operation.
"When Stepanek was bothered (by the crowd) I leant more on the fans. The noise helped me."
The winners will meet holders Spain or the United States in the final. Spain are 2-0 up after Friday's singles. (Reporting by Rex Gowar, editing by Pritha Sarkar and Ken Ferris)