Wikileaks founder Julian Assange addresses the press and supporters from the balcony of the Ecuadorian embassy in London.
Assange thanked the nation of Ecuador for taking a "stand for justice" in giving him political asylum, while warning that the US risked shunting the world into an era of journalistic oppression.
He appeared on the balcony of the South American country's embassy in London, where he has been taking refuge for two months as he seeks to avoid extradition to Sweden to face questioning on sexual assault allegations.
Assange thanked the leaders and people of Ecuador for supporting him and also staff at the London embassy "who have shown me hospitality and kindness, despite the threats we all received".
He thanked the governments and people of Argentina, Brazil and other Latin American countries who defended the right to asylum and people in the US, UK, Sweden and Australia who supported him in strength even when their governments did not.
"As WikiLeaks stands under threat, so does the freedom of expression and the health of all our societies. We must use this moment to articulate the choice that is before the government of the United States of America," he said.
"Will it return to and reaffirm the revolutionary values it was founded on or will it lurch off the precipice, dragging us all into a dangerous and oppressive world in which journalists fall silent under the fear of prosecution and citizens must whisper in the dark?
"I say it must turn back. I ask President [Barack] Obama to do the right thing: the United States must renounce its witch-hunt against WikiLeaks."
'Foolish talk'
There must be no "foolish talk" of prosecuting media organisations, be it WikiLeaks or be it the New York Times newspaper.
Assange also called on the US to end its "war on whistleblowers" and demanded that Bradley Manning, the US army intelligence analyst suspected of leaking the information, be released.
He has been charged with transferring classified data and delivering national defence information to an unauthorised source and faces up to 52 years in jail.
Assange described Manning as a hero and "an example to all of us", which drew cheers from scores of supporters.
"On Wednesday, Bradley Manning spent his 815th day of detention without trial," said Assange. "The legal maximum is 120 days."
Assange referred to recent jailings of people for exercising their freedom of speech and called for enthusiastic opposition to such oppressive actions.
"There is unity in the oppression. There must be absolute unity and determination in the response."
The Australian also thanked other helpful South American nations and supporters around the world, plus his family, including his children, "who have been denied their father".
He said: "Forgive me, we will be reunited soon."
Appearing to cheers
Assange emerged at the balcony at the embassy in Knightsbridge to loud cheers from his supporters.
He told them: "I am here today because I cannot be there with you today. But thank you for coming, thankyou for your resolve, your generosity of spirit.
"On Wednesday night, after a threat was sent to this embassy, the police descended on this building. You came out in the middle of the night to watch over it, and you brought the world's eyes with you.
"Inside this embassy in the dark, I could hear teams of police swarming up inside the building through its internal fire escape.
"But I knew there would be witnesses, and that is because of you.
"If the UK did not throw away the Vienna Conventions the other night, it is because the world was watching. And the world was watching because you were watching.
"So the next time that somebody tells you that it is pointless to defend those rights that we hold dear, remind them of your vigil in the dark before the embassy of Ecuador. Remind them how, in the morning, the sun came up on a different world, and a courageous Latin American nation took a stand for justice."
Earlier Assange's legal adviser, Baltasar Garzón, said Assange had instructed his lawyers "to carry out a legal action" to protect his rights.
Seeking asylum
He told media representatives outside the embassy: "Julian Assange has always fought for truth and justice and has defended human rights and continues to do so.
"He demands that WikiLeaks and his own rights be respected.
"Julian Assange has instructed his lawyers to carry out a legal action in order to protect the rights of WikiLeaks, Julian, himself, and all those currently being investigated."
Assange entered the building seeking asylum on June 19 and has been inside since.
Last week it was announced he had been granted political asylum, prompting a major diplomatic row between Ecuador, Sweden and the British government, which insists it is legally obliged to hand him over.
The foreign secretary, William Hague, has made it clear that Assange will not be allowed safe passage out of the country.
Assange denies the allegations he faces in Sweden and fears being transferred to America if he travels to contest them.
He enraged the US government in 2010 when his WikiLeaks website published tranches of secret US diplomatic cables. – © Guardian News and Media 2012