Prime Minister Julia Gillard, Attorney-General Nicola Roxon and Foreign Minister Bob Carr all sang from the same hymn sheet this week on the continuing legal saga of WikiLeaks publisher Julian Assange. But they chose their words very carefully.

The issue was whether the United States intends to charge and extradite Assange - the Australian journalist labelled by US Vice-President Joe Biden as ''a high-tech terrorist'' - with criminal offences for WikiLeaks' publication of hundreds of thousands of secret US military and diplomatic reports.

On Wednesday, the British Supreme Court rejected Assange's latest appeal against extradition to Sweden to be questioned about sexual assault allegations.

Assange, who rejects the Swedish allegations and has not been charged, fears extradition to Stockholm will make possible his extradition to the US to face espionage and conspiracy charges related to US private Bradley Manning's alleged leaking of a vast trove of classified information to the whistleblower site.

Well aware of successive polls that show a high level of support for WikiLeaks and Assange across the Australian political spectrum, the Australian government has been insistent this week that it has no knowledge whatsoever of any intention by the US to prosecute and extradite the WikiLeaks publisher.

Attorney-General Roxon took the lead on Tuesday, making the unequivocal claim in a letter to one of Assange's legal representatives that the government has ''no information from the United States to indicate that it has laid, or is about to lay, any charges against Mr Assange''.

Asked in a Senate estimates committee hearing on Wednesday whether the government had any knowledge of a secret US indictment, reported in a leaked email from the private US intelligence company Stratfor, Foreign Minister Carr similarly asserted: ''We have seen no evidence such a sealed indictment exists.'' Foreign Affairs and Trade Secretary Dennis Richardson dismissed the report as unconfirmed speculation.

Prime Minister Gillard followed the script in question time on Thursday, telling Parliament: ''At this stage we do not have any advice from the United States that there is an indictment against Mr Assange or that the United States has decided to seek his extradition.''

US ambassador Jeff Bleich also chimed in, saying the US had ''no interest whatsoever'' in Assange's extradition to Sweden, which was ''simply a matter for the UK and Sweden''.

For good measure the ambassador rejected as ''an invention'' claims that the US had issued a ''secret warrant'' for the arrest of Mr Assange. ''There is no such thing as a secret warrant. Period. They don't exist,'' Bleich said.

The choice of words was in many instances revealing.

Ms Gillard was careful to include the words ''at this stage'', and it appears from Wednesday's estimates hearing that Australian diplomats have studiously avoided asking whether charges have or are about to be laid.

A highly qualified lawyer, ambassador Bleich also knows a warrant is not the same thing as an indictment, which is the formal accusation of a crime issued by a US grand jury. Grand jury hearings are held in secret and an indictment may be sealed, that is kept secret, until an arrest warrant has been issued and the defendant taken into custody.

To say that secret warrants don't exist is true - but that isn't the point.

Carr implied the Swedish sexual assault investigation was the only matter Assange had to worry about, observing that the current extradition process was ''the only action he faces''.

All this is disingenuous to say the least.

Over the course of the past 18 months, Fairfax Media has pursued a series of freedom-of-information applications aimed at establishing the Australian government's knowledge of US investigations directed against WikiLeaks and Assange.

The Australian government has liaised closely with the US from the beginning of the US WikiLeaks investigation, which rapidly gathered steam following Bradley Manning's arrest in Iraq in March 2010. Last December, Fairfax obtained the release of cables from the Australian embassy in Washington, dated December 2010, that reported that WikiLeaks was the target of an ''unprecedented'' US criminal probe and that media reports that a secret grand jury had been convened in Alexandria, Virginia, were ''likely true''.

Despite extensive redactions, the released cables showed that the Australian embassy had confirmed through US officials that the US Justice Department was conducting an ''active and vigorous inquiry into whether Julian Assange can be charged under US law, most likely the 1917 Espionage Act''. The investigation was described by US officials as ''unprecedented both in its scale and nature''.

Australian diplomats also called on then US assistant attorney-general for national security David Kris to request ''advance warning of any public announcement of the results of US investigations or proposed actions''. Kris replied that he would take that ''reasonable'' request for advance warning ''up the line'', though he ''warned that advance notice sometimes caused problems later, when it became public that the government had been provided with advance warning''. The Australian diplomats said they would still appreciate advance notice ''so that ministers could respond appropriately''.

A more recent instalment of released cables shows the US and Australian governments continued high-level exchanges on WikiLeaks through last year.

The Washington embassy provided Canberra with updates including reporting on the issuing of subpoenas to compel WikiLeaks associates to appear before a grand jury in Virginia.

In December last year, the Washington embassy sent a representative to attend all seven days of private Manning's pre-court hearing. The embassy's report of the open court proceedings focused heavily on the prosecution's assertions that Manning had leaked to WikiLeaks ''and, specifically, to Julian Assange''.

These allegations, included that Manning ''indiscriminately and systematically'' data-mined classified US databases using WikiLeaks' ''Most Wanted List'' as a guide, that there was direct contact between Manning and Assange, and that WikiLeaks, and specifically Assange, assisted Manning's efforts to extract data without detection.

These US government allegations would presumably form the core of any potential espionage and conspiracy case against Assange.

At first glance, the First Amendment free speech provisions of the US constitution would appear to protect Assange as a journalist engaged in publication. However, the legal position is not clear-cut and there appears to be a widely held view among experts that a prosecution case could at least be constructed and pressed forward in spite of strong First Amendment arguments.

In an analysis published in December 2010, the US Congressional Research Service noted that the US Espionage Act applies to the ''receipt and unauthorised dissemination'' of classified US national defence information and that the law ''has been interpreted to cover the activities of foreign nationals overseas, at least when they take an active part in seeking out information''.

Any prosecution of Assange probably would focus not on WikiLeaks' publication but rather the circumstances of WikiLeaks' receipt of classified information and any advice or assistance Assange allegedly may have provided to Manning.

Such legal proceedings would probably run for years and end up before the US Supreme Court.

The scale of the WikiLeaks disclosures has been enormous, involving hundreds of thousands of US classified documents. No one should really doubt the desire of the US government to, as the Australian embassy in Washington put it, ''bring Assange to justice''.

Sealed indictment or not, the US will probably let Assange's Swedish legal issues play themselves out, before taking a final decision on whether to seek his extradition. Manning's court martial is scheduled to proceed in June - proceedings that presumably will reveal more of a potential prosecution case against Assange.

Meanwhile, ever anxious to demonstrate its loyalty to the US alliance, the Australian government has not uttered any objection to the prospect that Assange may be prosecuted for espionage.

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