WikiLeaks founder Julian Assange, who has been holed up at Ecuador's London embassy for five months, has a lung condition that could get worse, the South American country's envoy to Britain says.

"He has a chronic lung condition that could worsen at any time," Ambassador Ana Alban told reporters ahead of an annual gathering of Ecuador's diplomatic corps with President Rafael Correa in Quito.

Julian Assange addresses the United Nations General Assembly via videolink. Credit:AP

In an interview with CNN from Ecuador's embassy in London, the 41-year-old Australian refused to offer details about his condition, saying only: "I don't think it's important." He did not appear ill on camera.

Alban said Ecuador was "covering his medical expenses" and arranging "regular medical check-ups," noting that Assange has been living "in a confined space" since seeking asylum 162 days ago to avoid extradition to Sweden on charges of rape and sexual assault.