WikiLeaks founder Julian Assange is to deliver a message from the Ecuadorian Embassy to mark six months since he sought refuge inside the building.

The Australian is set to step onto the embassy's balcony for only the second time since he suddenly arrived on June 19 as part of his campaign to avoid extradition to Sweden.

The 41-year-old is wanted for questioning in Sweden over allegations of sexual assault, but he fears being sent to the United States to be quizzed over the WikiLeaks website for publishing top secret US government documents, including dossiers on the wars in Iraq and Afghanistan.

His supporters are expected to pack into the street outside the embassy in central London, close to Harrods in Knightsbridge, to hear his speech.

Mr Assange gave a speech from the balcony in August, watched by officers from the Metropolitan Police, which has mounted a round-the-clock guard on the embassy.

Police will arrest Mr Assange if he steps outside the embassy after he broke bail conditions.

The Ecuador Government has granted Mr Assange political asylum, but there has been no sign of a resolution to the impasse.

He gave a briefing to a handful of journalists last month, revealing that a block on processing donations by credit card companies to WikiLeaks had cost the whistle-blowing website over £30 million, with staff having to take a 40% pay cut as a result.

He described the block as an economic "death penalty" after the European Commission said it was unlikely to have violated EU anti-trust rules.

Mr Assange said WikiLeaks had lost 95% of its revenues, claiming that documents he had obtained showed that hard-right politicians in the United States were behind the blockade.