"Everyone knows that I was ill but I'm better now and my asthma is under control," said the Moroccan after a Golden League meeting in Zurich. "I still want to win gold in Athens."
El Guerrouj said in July he was considering not competing at the Olympics because of the mystery problems that were affecting his form and promised to make a decision after Friday's meet.
He suffered only his second defeat since the 2000 Sydney Olympics as he was edged into second place by Kenya's Bernard Lagat in Zurich. But El Guerrouj was not concerned by his performance, which ended an eight-year winning streak in Zurich.
"I'm actually very happy with the race. I ran very, very well," he said after taking 1.54 seconds off his own previous best for the season. "I hope to run like that again in Athens."
El Guerrouj's admission about his breathing troubles came days after his 29-race winning streak was brought to an end by Bahrain's Rashid Ramzi in the Rome Golden League meeting.
Since January, the world 1500 record holder has taken daily medication that left him struggling to maintain his full training programme.
He returned to winning ways with victory in Lausanne and followed that up with another triumph in Heusden Zolder, Belgium, before losing to the impressive Lagat on Friday.
The 29-year-old Kenyan believes he can repeat his winning performance over El Guerrouj in the Olympics after beating him at last.
"It was great preparation for the Olympic Games," Lagat said. "This was what I had wanted for a long time, to beat a great man like Hicham. I will be ready in Athens for any race, slow or fast."
But El Guerrouj, who became a father in June when his daughter Hiba was born, is determined to make 2004 a special year in his household by bringing home a 1500 gold medal.
"Hopefully, my daughter will be able to say: 'I was born in 2004, the year my father became an Olympic winner'."
The Athens Games run from August 13-29.
