The United States has provided assurances requested by the High Court in London which could finally pave the way for WikiLeaks founder Julian Assange to be extradited from Britain.

Last month, the High Court ruled that, without certain U.S. guarantees, Assange, 52, would be allowed to launch a new appeal against being extradited to face 18 charges, all except one under the Espionage Act, over WikiLeaks' release of confidential U.S. military records and diplomatic cables.

Those assurances — that in a U.S. trial he could seek a First Amendment right to free speech and that there was no prospect of new charges which could see the death penalty being imposed — have now been submitted by a deadline which fell on Tuesday.