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Assange, 41, whose website angered the United States by releasing thousands of secret diplomatic cables, has been holed up inside Ecuador's embassy in London since June to avoid extradition to Sweden for questioning over rape and sexual assault allegations. Assange has denied any wrongdoing.
"He has a chronic lung complaint that could get worse any time. The Ecuadorean state is covering Mr Assange's medical costs and we have arranged for regular doctor visits to check on his health," Ambassador Ana Alban told a local TV network during a visit to Quito.
British authorities say Assange will be arrested if he sets foot outside the embassy. The building, located just behind London's famed Harrods department store, is under constant police surveillance.
Ecuador said last month it is worried about Assange's health and asked Britain to guarantee him safe passage to hospital from the embassy if he needs medical treatment.
That would allow him to return to the embassy after treatment with refugee status.
Assange is said to be living a cramped life inside the modest diplomatic mission. He eats mostly take-out food and uses a treadmill to burn off energy and a vitamin D lamp to make up for the lack of sunlight.
In late August, the former computer hacker said he expected to wait six months to a year for a deal that would allow him to leave the embassy.