WikiLeaks chief Julian Assange says he has signed deals worth $1.5 million for his autobiography.

Mr Assange told Britain's Sunday Times newspaper the money will help him defend himself against allegations of sexual assault made by two women in Sweden.

"I don't want to write this book, but I have to," he said.

"I have already spent 200,000 pounds ($300,000) for legal costs and I need to defend myself and to keep WikiLeaks afloat."

The Australian says he will receive $800,000 from Alfred A Knopf, his American publisher, while a British deal with Canongate is worth $500,000.

He says money from other markets and serialisation is expected to raise the total to 1.1 million pounds ($1.5 million).

The latest project of Mr Assange's whistleblower website is the gradual release of tens of thousands of US diplomatic cables.

Since this latest project began, Mr Assange - who is on bail in Britain fighting a bid by Sweden to extradite him over the sex assault claims - has faced problems financing WikiLeaks.

Credit card companies Visa and MasterCard and Internet payment firm PayPal have blocked donations to WikiLeaks, prompting Mr Assange to label them "instruments of US foreign policy".

The Bank of America, the largest US bank, has also halted all transactions to WikiLeaks.

Washington has been infuriated by WikiLeaks as the site slowly releases the cache of around 250,000 secret US State Department cables.

The US is believed to be considering how to indict Mr Assange over the the huge leak.

Mr Assange has been staying at a friend's country mansion in eastern England since his release from jail on December 16 on strict bail conditions that include reporting to police daily and wearing an electronic tag.

A court in London is due to hold a full hearing on the Swedish extradition request starting February 7.

- AFP