WikiLeaks founder Julian Assange tonight said it was almost certain he would not leave his embassy refuge tomorrow to enter a British police station as part of his extradition process to be questioned in Sweden about sex-crime allegations.

Mr Assange has been holed-up in Ecuador's embassy in London since he made a surprise application for political asylum last week.

Earlier today, British police summoned Mr Assange to a London police station, demanding he leave the embassy.

But Mr Assange later told BBC television in a telephone interview: "Our advice is that asylum law both internationally and domestically in the UK takes precedence to extradition law, so the answer is almost certainly not."

Mr Assange, 40, risks being arrested the moment he steps outside the red-brick building after breaching bail terms, keeping both his supporters and police puzzled as to what he might do next.

Police said they had formally "served a surrender notice upon a 40-year-old man that requires him to attend a police station at date and time of our choosing".

"He remains in breach of his bail conditions, failing to surrender would be a further breach of conditions and he is liable to arrest," the police statement added.

The statement, in line with British policy, did not name the person but media quoted sources identifying him as Mr Assange.

The BBC reported the extradition unit delivered a note to Mr Assange and the Ecuadorean embassy. The embassy declined to comment.

Mr Assange denies any wrongdoing in Sweden and says he fears that if extradited there he could be sent on to the United States, where he could face criminal charges punishable by death.

Mr Assange enraged Washington in 2010 when his WikiLeaks website published secret US diplomatic cables.

Easily recognisable by his white-yellow hair, and known for his unpredictable behaviour, Mr Assange caused a media storm in Britain with his asylum bid.

Ecuador's ambassador has in the meantime flown home to discuss whether to grant him asylum but the decision has yet to be made.

By diplomatic convention, police cannot enter the embassy without authorisation from Ecuador.

But even if Quito granted him asylum, he has no way of travelling to Ecuador without passing through London and exposing himself to arrest.