Gao Zhen was sentenced to three years in prison, according to the US-based group Chinese Human Rights Defenders (CHRD), which reported last year that he had been indicted on charges of "insulting... heroes and martyrs."

The artist, who moved to the United States in 2022, was detained at his studio on the outskirts of Beijing during a visit to China in August 2024.

"We have significant concerns regarding the case, against Gao Zhen which we note was in connection with alleged actions taken years prior to the enactment of the law under which he was convicted," a US State Department spokesperson said.

Diplomats from the US embassy in Beijing and "several other diplomatic missions" had attempted to witness Gao's sentencing on Tuesday, but they were barred by courthouse authorities, the spokesperson said.

The public rebuke by Washington comes less than one month before US President Donald Trump is expected to host Chinese counterpart Xi Jinping for a closely watched state visit.

Gao Zhen, 70, and his brother Gao Qiang gained fame in the early 2000s for art touching on sensitive political topics such as the Cultural Revolution, the Tiananmen Square protests and the legacy of Mao, who led China from 1949 until his death in 1976.

Their works include a sculpture of the Communist leader kneeling, titled "Mao's Guilt," and another called "Execution of Christ," in which several bronze statues of Mao aim rifles at a statue of Jesus.

"The United States continues to support the right to freedom of expression, including as exercised through art," the State Department spokesperson said.