LONDON — WikiLeaks co-founder Julian Assange is unlikely to land on American soil any time soon as his legal team gears up for a drawn-out battle that centers on his freedom of speech.

The United States is seeking the extradition of Assange from Britain to face numerous charges for computer hacking and publishing classified material. The initial charge accused Assange of conspiring with former Army intelligence officer Chelsea Manning to crack a Department of Defense password, while another 17 charges under the Espionage Act were tacked on by the Department of Justice on Thursday.

Assange's lawyer, Jennifer Robinson, told NBC News she's preparing for "a big extradition fight" and argued, along with advocates in the U.S., that the latest indictment threatens the First Amendment.

"We are concerned about the free speech implications," she said. "This precedent will be used against other media organizations."

However, an extradition request related to a re-opened rape investigation in Sweden threatens to take priority.

Assange is being held in a London jail after being taken out of the Ecuadorian embassy in April and arrested for jumping bail after originally being accused of rape and sexual assault in Sweden in 2010.

Although there is a clear process for extradition from the U.K., experts say Assange's case is unique on a number of grounds and could pose a lengthy legal battle.

Assange's defense is likely to claim the charges are politically-motivated and violate his freedom of expression, protected by Article 10 in the European Convention on Human Rights, according to Michael Drury, a lawyer specializing in extradition cases for the London-based firm BCL Solicitors.

It stands to be a "highly unusual" argument in an extradition case, Drury told NBC News. Extradition cases more often see claims that a defendant would be treated inhumanely or harmed.

The U.S., Britain and European states also have a shared interest in the handling of state secrets since an agreement prompted by American officials to go after leakers was reached more than a decade ago, said Richard Aldrich, professor of international security at the University of Warwick. Countries are anxious about the possibility of journalists and groups like Wikileaks attaining and publishing secrets and intelligence online.

"This is all about trying to recover state secrecy," Aldrich explained. "The U.S. said we can’t do anything about the journalists, but we will go after the sources and the leakers vigorously."

In the past 10 years, more sources and whistleblowers have been prosecuted in the U.S. than previously through history, he said.

"There's a major campaign, people are being put away under the espionage act for potentially decades and the United States is determined to make an example of these people," he said.

Assange will likely find himself on trial in the U.S. where it will be up to the courts to decide whether he becomes one of those examples, Aldrich said, adding, "but exactly how that happens is difficult to predict."

The U.S. is almost always successful in extradition cases from Britain, Drury said.

British law requires the first hearing in an extradition case to be heard within 21 days of the order being filed. But given the complexity of the arguments, Drury said it could likely take up to a year for the case to be presented and delivered a verdict. If either side appeals the decision, it could extend the process another six to 12 months.

In the meantime, it's unlikely Assange will be granted bail because of the previous breach, said Drury.

With Swedish prosecutors announcing they have requested a detention order against Assange last week after reopening a sexual assault case against him, the entire U.S. extradition case could be further put on hold. Extradition is not normally a political decision, but Britain's home secretary has the power to suggest the courts prioritize one request over another.

Last month, dozens of British lawmakers signed a letter to Home Secretary Sajid Javid demanding he prioritize any extradition order made by Sweden.

British politicians wanting "to avoid being caught in the crossfire" of the American legal showdown would be enticed to hand Assange over to the Scandinavian nation, said Aldrich. "It’s more politically acceptable to extradite on the sorts of charges that the Swedes have raised."

But the political leadership in Britain is facing upheaval after Prime Minister Theresa May announced her resignation on Friday, adding to the uncertainty of which case would take priority. "We could have any one of 10 candidates in Downing Street in very short order and each person would take a different view on this," Aldrich said.

Even if Assange faces trial or is convicted in Sweden, Drury said he would eventually find his way back to British court to face the U.S. extradition order.

"Putting it entirely cynically, you can't get rid of the problem by sending him to Sweden," he said.