The international financial crisis has given world leaders a unique opportunity to create a truly global society, Britain's Prime Minister Gordon Brown will say in a keynote foreign policy speech today.

In his annual speech at the Lord Mayor's Banquet, Brown - who has spearheaded calls for the reform of international financial institutions - will say Britain, the United States and Europe are key to forging a new world order.

"The alliance between Britain and the US - and more broadly between Europe and the US - can and must provide leadership, not in order to make the rules ourselves, but to lead the global effort to build a stronger and more just international order," an excerpt from the speech says.