A seminar on Nato in Copenhagen has been cancelled after the US blocked an American academic who has criticised Donald Trump from attending.

The Danish Atlantic Council said it was "regrettably" no longer holding its event after Stanley Sloan, an expert in foreign policy, was apparently prevented from coming at the request of Carla Sands, the US ambassador to Denmark.

The seminar, on Nato and transatlantic relations, was sponsored by the US government.

Lars Bangert Struwe, head of the Danish Atlantic Council, said: "We have all the time known that Mr Sloan has a critical approach towards President Donald Trump. It is no secret -- especially when following his Twitter and Facebook profile."

However, he said that he had expected the contribution of Mr Sloan, a senior fellow at the Atlantic Council, to have been "unpolitical and objective".

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The US embassy in Copenhagen said on its Twitter account that his inclusion among the speakers at the Celebrating Nato's 70th Anniversary conference did not comply with the "agreement that we followed when recruiting all other speakers".

Mr Sloan responded in a series of tweets addressing the embassy, writing: "I'm sorry that you objected to my inclusion in the conference. I am an experienced public diplomacy lecturer who always represents his country well.

"I have served my country as an officer in the US Air Force, as a CIA intelligence analyst and manager, represented the US on the delegation to Mutual and Balanced Force Reductions in 1973, worked with Republicans and Democrats of all political persuasions for 24 years at the Congressional Research Service, and have many good friends in Denmark.

"I am certain I will be back, even if the US Embassy will not sponsor me. I look forward to returning to Denmark to talk about NATO, transatlantic relations, American democracy and freedom of speech."

In an email to Mr Sloan, quoted by Buzzfeed, Mr Struwe wrote that the embassy's actions were "in total disharmony with the way, the Danish Atlantic Council want to act".

He added: "Thus knowing that you do criticise the President of the United States, we believe that Freedom of Speech is paramount in every democracy, and we do not see a conflict between the Freedom of Speech and participating as a Speaker at an international conference.

"Having said that, the Danish Atlantic Council is not in a position, where we can ignore the given instructions by the Embassy of the United States, when the instructions are clear and specific."

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Ms Sands is a former actress, chiropractor and businesswoman who was appointed US ambassador to Denmark after donating almost $250,000 to Mr Trump's campaign.