The report issued on Monday said there were credible reports in Mexico of unlawful or arbitrary killings by police, military, and other officials; forced disappearance by government agents; as well as torture and inhuman treatment by security forces.
The report also stated that "impunity and extremely low rates of prosecution remained a problem for all crimes, including human rights abuses and corruption," and criticized violence against journalists in Mexico.
Asked about the report at a news conference, Lopez Obrador dismissed it, saying, "they're lying," and noted the U.S. "believes it's the government of the world."
"It's not worth getting angry about, that's just how they are," said Lopez Obrador, who is due to meet with former U.S. Secretary of State John Kerry in Mexico later on Tuesday. The report "is not true, they're liars."
State Department acting spokesperson Vedant Patel, speaking at a news briefing, rejected criticism that Washington was acting like "the government of the world" and doubled down on the findings of the human rights report.
"As it relates to Mexico, the reported involvement of members of Mexican police, military and other government institutions in serious acts of corruption and unlawful arbitrary killings remain a serious challenge for Mexico and that's why they were highlighted in our report," he said.
Lopez Obrador has pushed back against recent U.S. criticism of his record on security, which has come under increased scrutiny since the abduction of four American citizens in northern Mexico earlier this month. Two of them were later found dead.
The leftist president, who says he is rooting out corruption and impunity in Mexico, has argued his country is safer than the U.S. - despite a much higher murder rate - and criticized U.S. efforts to prevent dangerous drugs from entering the United States.
(Reporting by Dave Graham; additional reporting by Humeyra Pamuk in Washington editing by Jonathan Oatis)
