Bachelet, Brown, Lula da Silva and Stoltenberg will address the gathering Friday night to speak about charting a progressive path in response to the global economic crisis.
This is the most senior UK visit to Brazil since April 2009 when Gordon Brown went to see then President Lula in Brasilia, followed by a visit to Sao Paulo where he joined up with Peter Mandelson and a high-level business delegation.
Leaders saying they will attend include UK Prime Minister Gordon Brown, French President Nicolas Sarkozy and Brazilian President Luis Inacio Lula da Silva.