WikiLeaks founder Julian Assange's extradition to the United States from Britain was put on hold on Tuesday after London's High Court said the U.S. must provide assurances he would not face the death penalty.

U.S. prosecutors are seeking to put Assange, 52, on trial on 18 counts, all bar one under the Espionage Act, over WikiLeaks' high-profile release of confidential U.S. military records and diplomatic cables.

Assange's lawyers in February sought permission to challenge Britain's approval of his extradition, part of a more than 13-year legal battle in English courts.