He has sought refuge in this building just a stone's throw from Harrods because he is at risk of extradition to the United States to face conspiracy or other charges arising from WikiLeaks obtaining thousands of secret US military and diplomatic reports leaked by US Army soldier Bradley Manning.

Inside the embassy, which is little more than a small apartment in the central London suburb of Knightsbridge, the WikiLeaks chief spends his days in a small room of about 20 square metres.

The furnishing is not luxurious: a small conference table, a few chairs, a television, a notice board covered in Post-it notes, a bookshelf, a bed, an exercise treadmill, a sun lamp and, of course, several laptops. There is just one large window with heavy curtains preventing people from peering inside.

Mr Assange shares a kitchen with the embassy staff, and has made progress in Spanish.

There is no inclination to venture outside the embassy as British police are on guard 24 hours a day, waiting to arrest him so he can be extradited to Sweden to face questioning about sexual assault allegations.

Mr Assange is convinced extradition to Sweden would facilitate his extradition to the US but is confident the Swedish police inquiry will be dropped.

''The matters in Sweden are not serious,'' he said. ''However, the US case, the grand jury espionage investigation, is a very serious matter. Getting the US investigation dropped, that is our number-one priority. Otherwise I'll be watching my back for the next 30 years.''

Mr Assange dismissed reports that he was suffering from health problems due to his confinement, telling Fairfax he had ''no pressing health issues''.

However, Geoffrey Robertson, barrister and Assange's former legal representative, told ABC TV that after visiting him he thought Mr Assange had ''lost a bit of weight … [and] could do with some sunlight''.

Speaking to Fairfax, Mr Assange highlighted WikiLeaks' efforts to ''work around'' the financial embargo imposed on the transparency group by major credit card companies and electronic funds transfer agencies over the past two years.

He said the refusal of Visa, MasterCard, American Express and other companies to process direct donations amounted to an ''extraterritorial, extrajudicial financial death penalty'' that had robbed WikiLeaks of 95 per cent of the revenue stream it had enjoyed in late 2010. Mr Assange pointed out that some 40 per cent of the transparency group's funding still came from the US despite the hostility of the US government.

''We're fighting back, we've had some recent victories including in regard to tax deductibility for donations in the European Union,'' he said. ''We hope that new initiatives in the US will enable us to raise $1 million to cover our 2013 expenses.''

This week a new US media advocacy group, the Freedom of the Press Foundation, announced it would process credit card donations to WikiLeaks, the long established National Security Archive and two other groups devoted to ''journalism … dedicated to transparency and accountability.''

Mr Assange said he hoped to raise $US1 million ($A948,900) in a new fund-raising campaign.

Speaking in advance of a planned public address from the balcony of Ecuador's London embassy on Thursday evening (6am Friday, Melbourne time), Mr Assange expressed confidence that his transparency group's stocks were improving as he anticipates a run for a Senate seat in Australia's 2013 federal election. '' In Australia our support base has continued to grow, our supporters have been increasingly active. I hope that increasing organisational strength will flow into the election campaign.''