"Us black people are dying more than any other people in this planet," Maathai told a press conference in Nairobi a day after winning the prize for her work in human rights and reversing deforestation across Africa.
"It's true that there are some people who create agents to wipe out other people. If there were no such people, we could have not have invaded Iraq," she said.
"We invaded Iraq because we believed that Saddam Hussein had made, or was in the process of creating agents of biological warfare," said Maathai.
"In fact it (the HIV virus) is created by a scientist for biological warfare," she added.
"Why has there been so much secrecy about AIDS? When you ask where did the virus come from, it raises a lot of flags. That makes me suspicious," Maathai added.
"She said (HIV/AIDS) was invented as a bioweapon in some laboratory in the West," a senior State Department official said. "We don't agree with that."
The official pointed to a report of those comments published in August in Kenya's daily Standard newspaper, in which Maathai was quoted as saying that HIV/AIDS was created by scientists for the purpose of mass extermination.