Argentina coach Marcelo Bielsa resigned out of the blue on Tuesday, less than one month after steering the twice world champions to their first Olympic soccer gold medal.

Former Boca Juniors coach Carlos Bianchi was named as the favourite to replace the eccentric 49-year-old, who said he had run out of energy after six years in the high-pressure job.

"Today, I resigned as coach of the Argentina national team," the introverted Bielsa told a news conference.

"I realised the amount of energy which is absorbed by the various tasks which are involved in being coach of the team ... and that I didn't have this energy any more."

Bielsa had weathered Argentina's shock first round elimination at the 2002 World Cup followed by almost two years of non-stop criticism, only to leave at a moment when his team were playing some scintillating football.

Captain Roberto Ayala was caught cold by the announcement: "This news took me by surprise because I didn't notice anything at any time," he said in a radio interview.

Argentina Football Association (AFA) president Julio Grondona said he wanted to hire Bianchi, who won the South American Libertadores Cup three times in four years with Boca, the country's most popular club.

"The priority is Bianchi," said Grondona, who has less than one month to find a replacement before their next World Cup qualifier, at home to neighbours Uruguay on October 10.

Argentina's fortunes had changed for the better after Bielsa rebuilt the team, blending younger players such as forward Carlos Tevez and midfielders Javier Mascherano and Luis Gonzalez alongside established names like Cristian Gonzalez and Javier Zanetti.

His team played some excellent football at the Copa America in July before losing the final in unfortunate fashion to arch-rivals Brazil in a penalty shootout.

Bielsa, who was in charge for 68 matches, winning 42, drawing 16 and losing 10, then took the under-23 team -- including a number of the Copa America squad -- to the Athens Olympic Games where they won the gold medal in style with Tevez scoring eight goals.

They followed that up with a 3-1 away victory in Peru in a World Cup qualifier 10 days ago to leave them a comfortable second in the South American group and firmly on course for Germany in 2006.

BLACK SHEEP

Bielsa, who comes from a family of lawyers, is regarded as one of the most eccentric figures international football and the black sheep of the family.

His older brother Rafael is Argentina's Minister of Foreign Affairs.

Bielsa remained a mysterious and enigmatic figure throughout his reign.

He rarely shows emotion, even after his team play well, and often baffles the public with his long-winded, almost scientific explanations about his tactics. During matches, he paces up and down the touchline almost non-stop but rarely celebrates goals.

After an undistinguished playing career which was ended prematurely by a knee injury, Bielsa turned to coaching and was the surprise choice to replace Daniel Passarella after the 1998 World Cup.

Bielsa said that the low point came in Japan and South Korea where Argentina lost to England on the way to first-round elimination, having cantered through the qualifiers.

His team selections have often baffled the Argentine public.

He never allowed Hernan Crespo and Gabriel Batistuta to play together earlier in his reign and has been reluctant to give Javier Saviola an extended run in the team.