Julian Assange, the founder of the WikiLeaks website, has said that he will ignore a request by the police to give himself up because he fears that the US has secret plans to extradite him to Washington.

He said he had been advised that he was within his rights to ignore an extradition notice that was presented to him at the Ecuadorean embassy on Thursday.

During a telephone interview on BBC2's Newsnight, he was asked if he intended to give himself up. "Our advice is that asylum law both domestically and internationally in the UK takes precedence to extradition law, so the answer is almost certainly not," he said.

Assange has been asked to present himself to police on Friday to begin the process of extradition to Sweden over allegations of rape and indecency.

His refusal means that he will continue to take refuge in the embassy while the Ecuadorean government decides whether to accept his request for asylum. Even if they do so, Assange is likely to face a long stay at the embassy as he will be unable to leave without being arrested.

Assange said he had evidence that the US had secret plans to force him to face trial in America. "In the US, since at least the beginning of 2011, a US grand jury has been empanelled in Washington. It has been pulling in witnesses, forced testimony from those witnesses, subpoenaed records from Google, from Twitter," he said.

He submitted recordings to the BBC of American politicians and talkshow hosts calling for his death as evidence of the prejudice against him.

When asked if he had anything to say to the women who have accused him of rape and indecency, he replied: "I am simply not charged. That's all. That's all that is important in this matter. What has been said to date is sufficient."

Assange sought asylum in the Ecuadorean embassy last week after British courts upheld Sweden's right to request his extradition to answer the accusations made by two women he met while on a trip to Sweden. Both agreed to spend the night with him but later went to the police to complain about his behaviour. Assange left Sweden before he could be questioned by police.

Assange's supporters see the extradition as a cover for a subsequent extradition to the US to face charges over the release of diplomatic cables by WikiLeaks. A succession of British courts have found that Sweden has followed the correct procedure in issuing a European arrest warrant for Assange and ruled that Britain must comply with it.

Before the Newsnight interview, a police spokesman said: "The Metropolitan police have this morning, Thursday 28 June, served a surrender notice upon a 40-year-old man that requires him to attend a police station at a date and time of our choosing. This is standard practice in extradition cases and is the first step in the removal process."

He said Assange remained in breach of his bail conditions. "Failing to surrender would be a further breach of conditions and he is liable to arrest."

It is understood that Assange has been ordered to present himself at Belgravia police station at 11.30am on Friday.

This week, a letter signed by leading US figures in support of Assange's application for political asylum in Ecuador was delivered to the embassy. Among its signatories were film-makers Michael Moore and Oliver Stone, actor Danny Glover, authors Naomi Wolf and Noam Chomsky, comedian Bill Maher, and Daniel Ellsberg, the former US military analyst turned whistleblower, who leaked the Pentagon Papers in 1971.

Robert Naiman, policy director at the Just Foreign Policy campaign group, delivered the letter to the embassy on Monday, along with a petition signed by more than 4,000 Americans urging President Rafael Correa to approve Assange's request for asylum.

The letter, which has been posted online, states that its signatories believe Assange has good reason to fear extradition from the UK to Sweden "as there is a strong likelihood that once in Sweden, he would be imprisoned, and then likely extradited to the United States".

Adding that the US government "has made clear its hostility to WikiLeaks", it says Assange could face the death penalty in the US if he was charged and found guilty under the Espionage Act.

"We also call on you to grant Mr Assange political asylum because the 'crime' that he has committed is that of practising journalism," says the letter to Correa. "Because this is a clear case of an attack on press freedom and on the public's right to know important truths about US foreign policy, and because the threat to his health and wellbeing is serious, we urge you to grant Mr Assange political asylum."

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