Assange, 44, has spent the past three years at the Ecuadorian embassy in London, fearing extradition to the United States over espionage charges for publishing secret documents.
At a press conference Wednesday, Ecuadorian Foreign Minister Ricardo Patino said Ecuador asked Britain for a special "safe-passage" so that Assange could have an MRI scan because he has suffered "deep pain" in his right shoulder Since June.
"The British government is not offering the terms to make this happen," Patino said. "It's an additional fault in his protection, in the defense of a person's human rights."
"This is a person who needs to have exams done to understand the situation given it is grave. We don't know what he may have, and they don't want to give an authorization that they can perfectly well give."
The source of the pain is unknown, and can only be diagnosed with hospital equipment that cannot be brought into the embassy due to its size and weight, according to a letter from Assange's doctor, which Patino quoted.
The UK's Foreign and Commonwealth Office said on October 12 that it would not permit the safe passage to the hospital.
Patino protested that even in times of war and conflict, safe passage are given for humanitarian reasons to ensure that people receive the medical attention they need.