Ms Massi Fritz said in a text message sent to the Associated Press that "we are going to do everything" to have the Swedish case reopened "so Assange can be extradited to Sweden and prosecuted for rape".
The WikiLeaks founder is an Australia native, and the government said he would receive consular help due to its citizens after he was arrested on a USA conspiracy charge.
Assange, 47, has denied the sexual misconduct allegations, which he claims are politically motivated. Soon after his arrest, US authorities unsealed an indictment accusing him of conspiring with Army whistleblower Chelsea Manning, who leaked a trove of sensitive documents to WikiLeaks-including evidence of USA war crimes in Iraq and Afghanistan.
Following Assange's arrest in London on an unrelated US hacking charge, Clinton said that he should be held responsible.
After his dramatic arrest, he was taken to Westminster Magistrates' Court and found guilty of a British charge of breaching bail.
Assange, who founded the whistleblowing organisation Wikileaks, was dragged out of the embassy yesterday after Ecuador withdrew his right to asylum.
Democrats prepare border bills, say Trump enflames problem
Customs and Border Protection Commissioner Kevin McAleenan is due to take Nielsen's place on a temporary basis, starting April 10. There was no immediate reaction from the Department of Homeland Security or Trump on the ruling, which can be appealed.
"But the only extradition request is from US, because he's a whistle-blower on atrocities caused by USA military ops". People in power don't like that, so therefore we have to silence it. OK?
They will now re-examine the rape case to decide whether to resume it before the statute of limitations runs out in August 2020.
Labour leader Jeremy Corbyn has said Julian Assange should answer questions about sexual allegations.
But she said Assange should face the criminal justice system if the Swedish government charged him.
A witness who prosecutors were seeking to interview and an associate of Assange based in Europe who also requested anonymity said that before his arrest Assange had expressed concern that US prosecutors would also bring charges against him related to WikiLeaks' publication of Central Intelligence Agency computer hacking tools, which the website described as its "Vault 7" cache. He could be jailed for up to a year when he is sentenced at a later date.
In a tongue-in-cheek nod to Trump's hard-line immigration stance, Clinton added, "I do think it's a little ironic that he's the only foreigner this administration would welcome to the United States".
Previous comparable cases, involving accused hackers Lauri Love and Gary McKinnon, took between five and 10 years but eventually resulted in their extraditions to the United States being blocked.