Pompeo reserved his toughest criticism for China in a keynote speech at a Vatican conference on religious freedom. The others were Cuba, Iran, Pakistan and Myanmar.

“When the state rules absolutely, it demands its citizens worship government, not God,” he said.

“That’s why China has put more than one million Uighur Muslims … in internment camps and is why it throws Christian pastors in jail.

“When the state rules absolutely, God becomes an absolute threat to authority,” he said.

China has been widely condemned for setting up complexes in remote Xinjiang that it describes as “vocational training centres” to stamp out extremism and give people new skills.

“Today we must gird ourselves for another battle in defence of human dignity and religious freedom,” he said at the conference organised by the US embassy to the Vatican.

“The stakes are arguably higher than they were even during the Cold War, because the threats are more diverse and more numerous.”

Pompeo, who is due to meet Pope Francis on Thursday morning, later visited the Sistine Chapel and other parts of the Vatican museums.

His trip, which will also include a visit to his ancestral home in the rugged Abruzzo region northeast of Rome and stops in Montenegro, North Macedonia and Greece, has been overshadowed by an impeachment inquiry at home targeting President Donald Trump.