The Foreign Office rejected a request from Ecuador to grant Julian Assange diplomatic status, according to British officials.
The WikiLeaks founder has been living in the London embassy of the south American country for five-and-a-half years after being granted political asylum to fight allegations of sex-related crimes in Sweden.
Ecuador's foreign minister, Maria Fernanda Espinosa, said on Wednesday the country was seeking mediation to resolve the impasse.
However, an FCO spokesman said on Wednesday: "The Government of Ecuador recently requested diplomatic status for Mr Assange here in the UK. The UK did not grant that request, nor are we in talks with Ecuador on this matter.
"Ecuador knows that the way to resolve this issue is for Julian Assange to leave the embassy to face justice."
Swedish prosecutors have dropped their investigation into allegations against Assange, however he fears he will be extradited to the United States if he leaves the building and that there is a sealed indictment ordering his arrest.
Fernanda Espinosa, said: "No solution will be achieved without international cooperation and the cooperation of the United Kingdom, which has also shown interest in seeking a way out."
A United Nations panel concluded in 2016 that Assange was under arbitrary detention.
A statement by Assange's legal team said: "The UN ruling, issued almost two years ago, is crystal clear in its language. Mr Assange is unlawfully and arbitrarily detained by the UK authorities and must be released.
"The UK should not permit itself to be intimidated by the Trump administration's public threats to 'take down' Mr Assange."
Assange tweeted a picture of himself wearing an Ecuador national football short on Wednesday.