By Padraic Halpin

LONDON (Reuters) - The United States men's boxing squad were handed a dramatic lifeline late on Friday when a defeat that appeared to condemn the team to their worst result at an Olympic Games was overturned.

The Americans were facing an embarrassing exit after their last two fighters went out of the tournament, making it look like the once-great amateur boxing nation had failed to win a medal for the first time.

Officials, however, later overturned Errol Spence's defeat, meaning the team still have a chance of bettering the solitary bronze they won at Beijing four years ago.

Spence originally lost his second-round welterweight bout to world amateur bronze medalist Krishan Vikas of India 13-11.

After reviewing video footage, the International Boxing Association (AIBA) said in a statement that its competition jury found Spence should have been awarded four additional points for fouls committed by the Indian.

Spence, who told reporters earlier he thought he had won, is now the only U.S. male boxer of an original team of nine, competing across all bar one weight class, to make it beyond the last 16.

If he can win his quarter-final the U.S. will at least equal their performance in Beijing, deemed a calamity for the country that has captured a record 48 Olympic boxing golds won by the likes of Muhammad Ali, Joe Frazier and Sugar Ray Leonard.

As both losing semi-finalists get a bronze, Spence would be guaranteed a place on the podium with victory over Andrey Zamkovoy of Russia.

One medal would still be a big disappointment after the U.S. arrived in London with the biggest boxing squad and won their first four fights before losing eight in a row.

Their squad of fighters has suffered from haphazard preparations that saw Basheer Abdullah, an officer who ran the U.S. army's boxing program for 15 years, appointed head coach just weeks before the Games.

To further complicate matters Abdullah was forbidden from being at ringside because, having worked with professional boxers this year, he violates amateur rules.

U.S. executive director for boxing, Anthony Bartkowski, told Reuters on the eve of the Games that they had only recently introduced video analysis and sports science, expressing his surprise that it had not been implemented before.

Team captain Jamel Herring, eliminated earlier this week, told Reuters on Thursday the squad's training camp "wasn't the greatest" and that he hoped the experience would be a learning curve to get future programs back on track.

Three female fighters can also salvage some pride for the U.S. when they enter the fray on Sunday and Monday, the first time women will be allowed to box at an Olympics.

(Additional reporting by Patrick Johnston; editing by Tony Jimenez)