American diplomat Daniel Foote has now threatened to cut aid.
The Zambians, in response, say they intend to lodge a demarche – an official diplomatic complaint demanding action from the US president against his envoy.
Zambian President Edgar Lungu and America’s top diplomat in the country are at loggerheads over the jailing of two homosexuals under an archaic law which dates back to British colonial times.
Under the law, the men were jailed for 15 years for what is known as a crime against the order of nature – the legal term for gay sex in Zambia.
Mr Foote said he was “personally horrified” at the sentencing.
He went on to attack the government for failing to tackle endemic corruption and for giving poachers lighter jail terms – yet handing down harsh punishment on consenting homosexual adults.
But the Zambian president was far from cowed by the ambassador’s criticism.
Instead he went on the offensive, accusing Mr Foote of being “disrespectful” to the Zambian cultural and social values and interfering with the sovereignty of a foreign state.
President Lungu’s remarks on Sky News seem to have infuriated the ambassador even further.
The president said: “We know that there could be people who are homosexual in Zambia but we don’t want to promote it.
“We frown on it… the practice… most of us think it’s wrong… it’s unbiblical and unchristian… and we don’t want it.”
He went on: “Even animals don’t do it so why should we be forced to do it… because we want to be seen to be smart, to be seen to be civilised and advanced and so on.
‘If there are such countries which will allow bestiality, let them do it but not here.”
Hours later, the US ambassador told Zambian reporters: “I was shocked at the venom and hate directed at me and my country, largely in the name of Christian values, by a small minority of Zambians.”
He said he had received threats against him which has forced him to cancel official engagements to mark World Aids Day being organised for Tuesday.
“I am not qualified to sermonise,” the ambassador said, in what appeared to be a direct comment to the president.
“But I cannot imagine Jesus would have used bestiality comparisons or referred to his fellow human beings as ‘dogs’ or ‘worse than animals’, allusions made repeatedly by your countrymen and women about homosexuals.
“Targeting and marginalising minorities, especially homosexuals, has been a warning signal of future atrocities by governments in many countries.”
The ambassador insisted his country’s hundreds of millions of dollars in aid to Zambia gave him the right to express his views.
And he suggested if the authorities didn’t “renew and rejuvenate” its partnership with the United States, aid donations would suffer.
“If you see someone is not co-operating,” he said, ‘I think the natural inclination would be that assistance levels could change.”