WikiLeaks founder Julian Assange made his first public appearance since seeking refuge in the Ecuadorian embassy in London – and issued a defiant call to Washington to "renounce its witch-hunt" against his organisation.

The Australian yesterday appeared on the embassy's balcony – the first time he has been seen in public for two months – and urged the US government to "reaffirm the revolutionary values it was founded on".

Assange, who is wanted in Sweden for questioning on sexual-assault allegations, thanked Ecuador for taking a "stand for justice" in giving him asylum.

The decision has led to a diplomatic stand-off involving Ecuador, Sweden and Britain, which insists it is legally obliged to hand him over.

Foreign Secretary William Hague has made clear Assange will not be allowed safe passage out of the country. Assange denies the allegations and fears being transferred to America if he travels to contest them.

Assange enraged the US government in 2010 when WikiLeaks published tranches of secret US diplomatic cables.

Yesterday he thanked Ecuador and 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."

Earlier, his legal adviser Baltasar Garzon said Assange had instructed his lawyers "to carry out a legal action" to protect his rights.

Mr Garzon told media representatives: "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, who entered the building seeking asylum on June 19, thanked supporters who went to the embassy on Wednesday night, when it emerged Britain had warned the Ecuadorian government that the diplomatic status of the embassy could legally be revoked.

He said: "Thank you for coming, thank you 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."

He added: "We must use this moment to articulate the choice that is before the government of the United States of America.

"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 Obama to do the right thing: the United States must renounce its witch-hunt against WikiLeaks."

He also called on the US to end its "war on whistleblowers", and demanded the release of Bradley Manning, a US army intelligence analyst suspected of leaking information, who is being held at an American military base.

Manning 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 him as a hero and "an example to all of us".