WikiLeaks founder Julian Assange has launched a legal bid to force US President Donald Trump to disclose charges “secretly filed” against him.

In an attempt to head off a possible extradition to the US, lawyers for the Australian activist have urgently requested the Washington-based Inter-American Commission of Human Rights (IACHR) to intervene in the case.

A 1172-page application was submitted to the IACHR on Thursday (Australian time), when his stay at a central London apartment has been made increasingly untenable by a new Ecuadorian government.

A mistake in a legal document filed by the US authorities in an unrelated case hinted that criminal charges may have been prepared in secret.

The application by Assange’s lawyers identifies a raft of legal obligations that the US and Ecuador are “flouting” in their treatment of him.

The lawyers claim the Trump administration has been attempting to “pressure” Ecuador to hand over Assange, including “serious overt threats” against Ecuador made by senior US political figures.

“Ecuador is required to end the regime of isolation imposed on Mr Assange, suspending the application of the so-called special protocol and guaranteeing his rights as an asylee will be respected in full,” the document filed by his lawyers stated.

The Department of Justice confirmed in November last year that the Trump administration filed sealed charges against Mr Assange.

However, with the news only becoming public due to a government slip-up, the details of the charges aren’t yet known as Mr Trump is accused of refusing to reveal them.

“The revelation that the US has initiated a prosecution against Mr Assange has shocked the international community”, the legal submission stated.

The US government is required to “provide information as to the criminal charges that are imputed to Mr Assange in full,” it added.

The submission said that for the first time, US federal prosecutors have formally approached people in the US, Germany and Iceland in recent months and pressed them to testify against Mr Assange in return for immunity from prosecution.

Baltasar Garzon, the international co-ordinator of Assange’s legal team, said he was asking the IACHR to make an urgent intervention in Assange’s favour.

Mr Garzon said he was calling for international solidarity for this case, in which the right to access and impart information freely was in jeopardy.

-with AAP