Western leaders should set aside their differences with Russia over Ukraine to focus on the growing threat of Islamic extremism, former British prime minister Tony Blair said on Wednesday.
In a speech in London, the Middle East envoy said the spread of extremist ideology in that region as well as in Pakistan, Afghanistan and North Africa "represents the biggest threat to global security of the 21st century".
"On this issue, whatever our other differences, we should be prepared to reach out and cooperate with the East, and in particular, Russia and China," Blair said.
His comments come amid a precarious Cold War-style standoff between Moscow and the West over Ukraine.
Blair said there was a shared interest between East and West on the dangers of religious extremism and it should be at the top of the global agenda.
He said many people were "curiously reluctant" to acknowledge the common thread linking Islamist movements around the world, but said "we have to take sides" against a dangerous ideology that was a "perversion" of Islam.
"There is a Titanic struggle going on within the region between those who want the region to embrace the modern world -– politically, socially and economically -– and those who instead want to create a politics of religious difference and exclusivity. This is the battle," Blair said.
Taking sides meant supporting the principles of religious freedom and open rules-based economies, whether they were held by states or revolutionaries.
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In reality, this meant backing the new governments in Egypt and Tunisia and helping the security services in Libya and Yemen to reform, he said.
In Syria, which he called "an unmitigated disaster", Blair said both the prospect of President Bashar al-Assad staying in power and the opposition taking over seemed like "bad options".
"Repugnant though it may seem, the only way forward is to conclude the best agreement possible even if it means in the interim President Assad stays for a period," he said.
He also said it was an "absurdity" that Western nations spent so much on defending themselves against Islamist extremism that was being taught to young people in countries "with whom we have intimate security and defence relationships".
Blair suggested the G20 launch an international programme to eradicate religious intolerance from schools systems and civil society organisations in those countries.
"They need us to make this a core part of the international dialogue in order to force the necessary change within their own societies," he said.
"This struggle between what we may call the open-minded and the closed-minded is at the heart of whether the 21st century turns in the direction of peaceful co-existence or conflict between people of different cultures."
Blair was prime minister between 1997 and 2007 and is now representative for the Middle East Quartet, comprised of the United Nations, the European Union, the United States and Russia.