The Nato alliance, stretched by operations in Afghanistan, should further expand its role to include counter-terrorism, cyber-security and the security of natural resources, according to a classified document to be endorsed by presidents and prime ministers next week.

At a summit in Riga, Latvia, that begins on Tuesday, leaders including US President George W. Bush, France's President Jacques Chirac and Tony Blair, British prime minister, will give their backing to an attempt to update and revise Nato's strategy for the 21st century.