During a press conference from the Ecuadorian embassy in London, Mr Assange said there would be "many discussions" before Manning leaves prison in May.
The WikiLeaks founder also welcomed Barack Obama's decision to free the ex-soldier who handed over classified documents.
Speaking this evening, Mr Assange said: "I stand by everything I said, including the offer to go to the United States if Chelsea Manning's sentence was commuted.
"It is not going to be commuted until May – we can have many discussions to that point.
"I have always been willing to go to the United States provided my rights are respected."
Julian Assange will stand by an offer to be extradited to the US
AFP • GETTY
Julian Assange said there would be 'many discussions' before Chelsea Manning's release
Mr Assange also claimed there had been a seven-year long attempt in America to build a prosecution case against him and whistleblowing site WikiLeaks.
He said if it took him going to the US to "flush out" the case being prepared against him, or to drop it, then "we are looking at that".
Ms Manning's sentence was commuted by outgoing President Mr Obama in one of his final acts as US President.
The WikiLeaks founder welcomed Barack Obama's shock decision
Mr Obama announced the former soldier's sentence would be reduced from 35 years to seven years during his last White House press conference on Tuesday.
The shock news called Julian Assange's bluff who had pledged to agree to US extraditon after more than four years of being holed up in the Embassy of Ecuador in London.
Earlier this month WikiLeaks tweeted: “If Obama grants Manning clemency Assange will agree to US extradition despite clear unconstitutionality of DoJ [Department of Justice] case.”
Barack Obama commuted Chelsea Manning's sentence is his last White House press conference
Last November Mr Assange was interviewed in the presence of prosecutors from Sweden, where he faces a sex allegation.
He denies the claims, but insists he faces extradition to the United States for questioning over the activities of WikiLeaks if he leaves the embassy.
Mr Assange said the UK's Crown Prosecution Service had refused to confirm or deny whether there was an extradition request from the US.
He said he loved what WikiLeaks was doing, adding it had published more than 10 million documents that had never been made public before, which had contributed to justice and led to innocent people being released from prison.