Washington: Striving to get Edward Snowden back to America, US, Attorney General Eric Holder has assured the Russian government the US has no plans to seek the death penalty for the former National Security Agency systems analyst.

In a letter dated Tuesday, the attorney general said the criminal charges Snowden now faces in this country do not carry the death penalty and the US will not seek his execution even if he is charged with additional serious crimes.

Holder’s letter followed news reports that Snowden, who leaked details of top secret US surveillance programmes, has filed papers seeking temporary asylum in Russia on grounds that if he were returned to the US he would be tortured and would face the death penalty.

Snowden has been charged with three offences in the US, including espionage, and could face up to 30 years in prison if convicted.

The attorney general’s letter was sent to Alexander Vladimirovich Konovalov, the Russian minister of justice.

Holder’s letter is part of a campaign by the US government to get Snowden back. When Snowden arrived at Moscow’s international airport a month ago, he was believed to be planning simply to transfer to a flight to Cuba and then to Venezuela to seek asylum.

But the US cancelled his passport, stranding him. Besides applying for temporary asylum in Russia, he has said he would like to visit the countries that offered him permanent asylum - Venezuela, Bolivia and Nicaragua.

Some Russian politicians, including parliament speaker Sergei Naryshkin, have said Snowden should be granted asylum to protect him from the death penalty. If Snowden were to go to a country that opposes the death penalty, providing assurances that the US won’t seek it could remove at least one obstacle to his return to America.

“I can report that the United States is prepared to provide to the Russian government the following assurances regarding the treatment Mr Snowden would face upon return to the United States,” Holder wrote. “First, the United States would not seek the death penalty for Mr Snowden should he return to the United States.” In addition, “Mr Snowden will not be tortured. Torture is unlawful in the United States.”

Bruce Fein, a lawyer representing Edward Snowden’s father, criticised Holder.

“Today the attorney general stated - apparently thinking he was being conciliatory - that if Edward Snowden were returned to the United States we wouldn’t kill him or torture him. Those are concessions only in the mind of someone who’s very biased,” said Fein.

He said an impartial prosecutor would have said that Snowden is entitled to a presumption of innocence and that he would guarantee Snowden a fair trial by ensuring it was held in a venue that wasn’t populated by NSA contractors.

The attorney general said that if Snowden returned to the US he would promptly be brought before a civilian court and would receive “all the protections that United States law provides”.

“We understand from press reports and prior conversations between our governments that Mr Snowden believes that he is unable to travel out of Russia and must therefore take steps to legalise his status. That is not accurate, he is able to travel,” Holder added.

Despite the revocation of Snowden’s passport on June 22, he remains a US citizen and is eligible for a limited validity passport good for direct return to the US, said the attorney general.

Snowden, who is believed to have been staying at the Moscow airport transit zone since June 23, applied for temporary asylum in Russia last week.

A spokesman for President Vladimir Putin said Russia has not budged from its refusal to extradite Snowden. Said Dmitry Peskov told Russian news agencies that “Russia has never extradited anyone and never will.” There is no US-Russia extradition treaty.

Peskov also said that Putin is not involved in reviewing Snowden’s application or in discussions with the US of his future with the US, though the Russian Security Service, the FSB, had been in touch with the FBI.

Snowden has not overtly threatened to release more damaging documents, though a journalist with whom he has been working, Glenn Greenwald, has said that blueprints detailing how the NSA operates would be made public if something should happen to Snowden.

Putin has said that if Snowden releases any more of the materials, Russia will not grant him temporary asylum.

There’s little chance Snowden will be able to use what information he has as a bargaining chip to negotiate his prosecution or extradition.

The government must take the position: “We don’t negotiate with extortionists,” said Michael Chertoff, the former head of the Justice Department’s criminal division and former secretary of homeland security. Chertoff said he can’t recall a case in which the US government has caved under this type of threat.

US officials have said what Snowden already has released will harm national security, though it’s too early to tell what damage has been done. The US intelligence community has a good idea of what other documents he has.