The bloody Syrian conflict could have been resolved four years ago had Western powers listened to Russia, former Special Envoy Lakhdar Brahimi has said.

The Algerian diplomat, who was the United Nations and Arab League Special Envoy to Syria, said a Russian offer to force President Bashar al-Assad to step aside in 2012 was a missed opportunity for peace.

He said there were “no good guys in the Syrian tragedy” and, speaking to Al Jazeera English, he condemned Western powers and Muslim nations for their failure to put “the interest of the Syrian people as their first priority”.

Ambassador Brahimi, who resigned as the UN envoy in 2014 in frustration at his inability to bring about a coherent international strategy to bring peace to Syria, placed “a lot of blame on the outside forces, the governments and others who were supporting one side or the other”.

Iran, Saudi Arabia, Iran and the rest of the “Muslim world” were, he said, as much to blame as anyone.

“Everybody is to blame,” Ambassador Brahimi told Mehdi Hasan, the host of UpFront. “The entire world. What did the Americans do? What did the French do? What did the British do?”

Martti Ahtisaari, the former Finnish president, revealed last year that in 2012 the Russians had offered to force President Assad to step down as part of a peace deal.

The proposal was put to the UN Security Council but, said Mr Ahtisaari, Britain, France and the US were so convinced Assad was about to fall anyway they disregarded the offer.

Ambassador Brahimi has now spoken out to back the Finn’s claim that the offer represented a missed opportunity and that the war “could have been solved”. Since the deal was offered, tens of thousands of people have been killed in the war and millions more have fled their homes.

“The Russians had a much more realistic analysis of the situation than practically anybody else,” he maintained. “Everyone should have listened to the Russians a little bit more than they did.”

While blaming everyone connected to the conflict, he added that President Assad was the most culpable: “There’s no doubt that the number one man must bear number one responsibility for what has happened.”

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Describing Syria as “probably not a failed state, but certainly not a functioning state,” he said that President Assad remains part of the solution. However, he added, that “being part of the solution does not mean he’s going to govern for another 40 years”.

When Mr Brahimi resigned in 2014, the UN General Secretary Ban Ki-moon, the UN secretary general expressed his deep regret and said the inability to win peace in Syria was “a failure for all of us”. He described him as “one of the world’s most brilliant diplomats.”