Ecuador's President Rafael Correa has said the United Kingdom would be committing diplomatic suicide if it tried to enter his country's embassy in London to arrest Julian Assange.
Speaking on state television, Mr Correa said: "It would be a suicide for the United Kingdom to enter the Ecuadorian Embassy.
"It will be a precedent that would allow later on for the diplomatic premises of this country [the UK] in other territories to be violated in every corner of the planet."
South America's foreign ministers have met in Ecuador to discuss the case of WikiLeaks founder Julian Assange. They condemned Britain's threat to forcibly enter the Ecuadorean embassy in London:
– Ali Rodriguez, Secretary-General of the Union of South American Nations
We would to express our solidarity and our support for the government of Ecuador in the face of the threats made by the UK against the building that shelters its diplomatic mission. We reiterate the right of any state to grant asylum. We condemn the threat of using force from one state to another as well as reminding everybody of the full validity of the principles gathered by international laws, the respect of each state's sovereignty and the respect of all international treaties.
Before Julian Assange came out onto the Ecuadorian embassy's ground-floor balcony, well-known supporters gave speeches in front of the media.
Craig Murray, former UK ambassador to Uzbekistan and whistleblower on the CIA's "extraordinary rendition" programme, said:
Even during the height of the tensions of the Cold War, the opposing parties never entered each other's embassies to abduct a dissident.
The fact that William Hague openly threatened the Ecuadorians with the invasion of their sovereign premises is one further example of the total abandonment of the very concept of international law by the neo-conservative juntas that are currently ruling the former Western democracies.
The WikiLeaks founder Julian Assange has called on the United States to stop what he called its "war on whistleblowers".
He spoke from the balcony of Ecuador's London embassy, appearing in public for the first time since he sought asylum there two months ago.
But Mr Assange did not speak about the attempts to extradite him to Sweden to face sexual assault charges.
ITV News' Political Correspondent Alex Forrest reports:
Police presence and crowds gathered outside the Ecuadorian embassy in London, waiting for WikiLeaks founder Julian Assange to make an address from inside the building.
Julian Assange said: "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."
In a speech delivered from the balcony of the Ecuadorian embassy, Julian Assange has called on the United States to "end its witch hunt" against the WikiLeaks organisation.
Praising the support and dedication of his supporters, Julian Assange also thanked those who had helped him with his goal of being granted asylum.
Addressing his supporters, he said: "I am here today because I cannot be there with you today.
"Thank you for coming, thank you for your resolve, your generosity of spirit.
"On Wednesday night, when a threat was sent to this embassy and police were sent to this building, you came to watch over it.
"Inside this embassy after dark, I could hear police swarming through the building.
"But I knew there would be witnesses."
WikiLeaks founder Julian Assange today said he had taken a "stand for justice" and praised the "courageous South American nation" of Ecuador as he spoke from the country's embassy balcony in London during his first public appearance for two months.