The West must put aside differences with Russia over Ukraine to focus on tackling the threat from radical Islam, Tony Blair is set to warn.
Failing to "take sides" with moderates in the Middle East and North Africa could mean the 21st century is dominated by conflict rather than peaceful co-existence, he will say.
Mr Blair is due to make the intervention in a speech at Bloomberg in London this morning.
It comes with tensions still running high in eastern Ukraine, and after Russia was jettisoned from the G8 group of nations over Vladimir Putin's decision to annexe the Crimea.
But Mr Blair will describe a wider crisis with its roots in "a radicalised and politicised view of Islam, an ideology that distorts and warps Islam's true message".