Dressed in a blue button-down shirt and a red tie, Assange looked out over a throng of supporters and police in front of the embassy to deliver about 10 minutes of remarks, first addressed to those on scene and then to political figures including U.S. President Obama.

"I am here today because I cannot be there with you today, but thank you for your resolve, for your generosity of spirit," Assange said.

"On Wednesday night after a threat was made on this embassy and police descended on this embassy, you came out to watch over it."

Assange said that he could hear police swarming up through the fire escapes of the embassy, and said "If the U.K. did not throw away the terms of the Vienna convention it was because the world was watching and the world was watching because you were watching."

"As WikiLeaks stands under threat, so does the freedom of expression and the health of all of our societies," Assange said.