An international law professor says that Ecuador could take Britain to the International court of law if it enters their embassy without permission.

Britain has threatened to raid the Ecuadorian embassy in London if WikiLeaks founder Julian Assange is not handed over, Ecuador's foreign minister says.

Ecuador says it wants to give the Australian asylum, but the British government is refusing to provide him with safe passage, meaning he will be arrested as soon as he leaves the Ecuadorian embassy where he fled to several months ago.

At a media conference in Quito, Ecuador's foreign minister Ricardo Patino said the position taken by the British government was "unacceptable".

"Today we've received a threat by the United Kingdom, a clear and written threat that they could storm our embassy in London if Ecuador refuses to hand in Julian Assange," he said.

"We are not a British colony."

Mr Patino said a decision on the WikiLeaks founder's asylum request would be made public late tonight.

Don Rothwell, Professor of International Law at the ANU, told ABC 720 the threat to raid the embassy is very surprising.

"Under international law the Ecuadorian embassy in London enjoys protections under the Vienna convention on diplomatic relations. Under those conventions the UK authorities are not permitted to enter without invitation," Professor Rothwell said.

"The UK government has effectively indicated to Ecuador that if the matter isn't resolved to their satisfaction they are reserving the right to unilaterally enter the embassy and presumably arrest Mr Assange."

"There is a UK law that allows that, but it was a law that was enacted in the 1980s in response to a number of events concerning the Libyan embassy in London."

"It was proven to be supporting terrorist activities."

"I do not see anything, on the basis of the facts before us, which suggests that Mr Assange's case would justify a revocation of that protection."

"This is really a very significant ramping up of the pressure upon Ecuador by the UK and it's not surprising that Ecuador has reacted in the way that it has."

The British Foreign Office said it was "determined" to extradite Mr Assange to Sweden.

"The UK has a legal obligation to extradite Mr Assange to Sweden to face questioning over allegations of sexual offences and we remain determined to fulfil this obligation," said a UK Foreign Office spokesman.

Mr Assange is trying to avoid extradition to Sweden, where he is wanted for questioning over sexual assault allegations made by two WikiLeaks supporters in 2010.

The Australian activist says he had consensual sex with the women.

Mr Assange, who enraged Washington in 2010 when his WikiLeaks website published thousands of secret United States diplomatic cables, says he fears he could be sent to the US, where he believes his life would be at risk.

In the past he has appealed for the Australian Government to intervene, but the Federal Attorney-General Nicola Roxon told Radio National there is little Australia can do.

"We've certainly made diplomatic contact and we've obviously been providing consular support as well but ultimately, I think you and your listeners would understand that this is a matter between Mr Assange and Ecuador," she said.

"Increasingly it seems it's a matter between Ecuador and the UK."

Professor Rothwell said the threat by the UK will be viewed seriously by governments around the world.