Mikhail Gorbachev gave a stark warning after soaring animosity between the two powerful nations that has seen the Kremlin openly threaten to shoot down Western aircraft.
Mr Gorbachev spoke of his fears to state news agency RIA Novosti as comparison were drawn with the worst crises of the Cold War.
The 85-year-old said: “I think the world has reached a dangerous point.
“I don’t want to give any concrete prescriptions but I do want to say that this needs to stop. We need to renew dialogue. Stopping it was the biggest mistake.”
Talks over Syria were suspended by the US on October 3 when Russia was accused of tearing up a ceasefire deal to launch a brutal aerial assault on rebel strongholds in Aleppo.
In 2014 he blamed American “triumphalism” for fuelling what he warned could become a “new Cold War.”
Since the collapse in relations Russian media has speculated around the dangers of all-out war with the US, while public figures have compared the confrontation over Syria with the Cuban Missile Crisis.
US Secretary of State John Kerry said Russia and the Syrian government to be investigated for war crimes.
The relentless campaign in Aleppo has also drawn criticism from other nations as France’s foreign minister mimicked Kerry’s call on Monday.
Russia then accused the US of “unfriendly” actions, and deployed nuclear-capable missiles to its Baltic exclave of Kaliningrad.
Mr Putin’s country also warned it would shoot down Western aircraft if the US launched retaliation airstrikes against pro-government targets in Syria.
The Russian premier also pulled out of an arms-control agreement aimed at reprocessing weapons-grade plutonium.
Mr Putin also demanded the US step back its military commitment to Nato members in eastern Europe, claiming the expansion of the alliance had threatened his country’s security.
Mr Gorbachev said: “It is necessary to return to the main priorities. These are nuclear disarmament, the fight against terrorism, the prevention of an environmental disaster.
“Compared to these challenges, all the rest slips into the background.”
Mr Gorbachev, who ruled the Soviet Union from 1985 until it broke up in 1991, is widely credited with ending the Cold War and building the architecture of nuclear arms control in a series of summits with Ronald Reagan.
He also played a crucial role in the fall of the Berlin Wall, a symbol of communism in the decades following the Second World War.
His calls over ending the “dangerous” breakdown between Russia and America have been widely echoed.
German foreign minister, Frank-Walter Steinmeier, warned last week: “It’s a fallacy to think that this is like the Cold War.
“The current times are different and more dangerous.”
Although Russia is showing no signs of backing down after revealing it plans to expand its current naval facility at the Syrian post of Tartus into a “permanent” base.
The news came shortly after Russian parliament ratified a treaty allowing indefinite deployment of Russian forces to the country.
Russia is reportedly sending 5,000 paratroopers to take part in joint exercises in Egypt later this month, in a move that signifies Middle Eastern ambitions well beyond Syria.
Moscow and Cairo are discussing options for renting several bases, including the Soviet-era air base near Sidi Barrani, Izvestia, a pro-government daily paper, reported on Monday.