WIKILEAKS founder Julian Assange's bold bid for asylum in Ecuador may well pay off, an Australian expert believes.

Mr Assange walked into Ecuador's embassy in London on Tuesday and sought political asylum in a last-ditch effort to avoid extradition to Sweden to face sex-crime allegations he says are baseless.

The Australian-born 40-year-old fears removal to Sweden could pave the way for extradition to the US to face possible charges - and a possible death sentence - over WikiLeaks' release of thousands of diplomatic cables.

Ecuador's leftist government, which has expressed support for Mr Assange, says it is weighing his application, which comes just days after Britain's Supreme Court re-endorsed its decision to allow his extradition to Sweden.

Australian National University international law expert Donald Rothwell says the bid could work.

"He's made a calculated judgment that on the basis of his interactions with the Ecuadorian government that he's fairly confident he will be granted asylum by this particular country," Professor Rothwell said.

"But ultimately whether Ecuador grants him asylum is a political judgment based on whatever arguments or evidence Mr Assange is able to put to support his case."

Ecuadorian asylum would put him beyond the reach of Sweden and possibly also the US, Prof Rothwell says. Ecuador has an extradition treaty with the US, but it excludes those wanted on political charges.

Senior Amnesty International executive Widney Brown says Mr Assange has the right to seek asylum but questions whether he really has a well-founded fear of persecution.

"He's going to have to meet a threshold it's not clear to me he would be able to meet, since he has had his day in court," Ms Brown told reporters in Canberra.

Prime Minister Julia Gillard said government officials would endeavour to make contact with both Mr Assange and the Ecuadorian government.

Asked whether her government would resist any US extradition attempts, she said she would not comment on hypotheticals.

"But let's be very clear about this: Australia opposes extradition in death-penalty cases and we do that for every Australian citizen," Ms Gillard told reporters in Mexico.

Australian Greens senator Scott Ludlam said he had seen part of a letter Mr Assange wrote to the Ecuadorian government about his case.

"He doesn't have any confidence at all in the Australian government's willingness to protect him, or to stand up for his rights," Senator Ludlam told reporters in Canberra.

Mr Assange's mother Christine says she desperately hopes Ecuador will protect her son.

"I hope the Third World can stand up for what's morally right when the First World can't and won't because they've got their snouts in the trough, rolling over for US greed and big business," she said.