The recent breakdown of the US-Russian ceasefire in Syria is not the first time that Moscow’s and Washington’s peace efforts have failed. However, this time there is a difference.

In February and March, the failure of the truce was due to the actions of the Syrian parties. Russia and the US still offered some hope that they could work things out together. Not any longer. The current breakdown resulted from the bombing of Syrian government forces at Deir Ezzor, which the US recognised as a “mistake”, and the attack on a humanitarian convoy in Aleppo, for which the Americans blamed Russia.

Rather than being contained, the situation was exacerbated by Russian support for the Assad forces in their offensive in Aleppo, and by condemnation by the US and its allies of those actions as “war crimes”.

In response to American criticism, Vladimir Putin, president of Russia, suspended the 2000 agreement with the US on the use of plutonium. By itself, the plutonium issue is relatively minor and Moscow’s concerns are not new. What is important is that the demise of that agreement further narrows the basis of US-Russian nuclear arms control. With the Nunn-Lugar co-operative threat-reduction programme terminated, the next agreement to fall could be the Intermediate-Range Nuclear Forces Treaty, long under attack in both the US and Russia.

Mr Putin has chosen to emphasise the subject of nuclear weapons because he knows it is one that cannot be ignored. He has added to it a list of issues that Moscow sees as obstacles to normal relations with Washington — from the expansion of Nato’s military infrastructure in central and eastern Europe to the economic sanctions imposed by the Magnitsky Act, passed by the US Congress in 2012.

Hardly anyone in the Kremlin really believes that these obstacles can be removed in the foreseeable future. Instead, the issues have been spelt out to counter US demands on Russia relating to Ukraine and Crimea. Rhetorically, at least, this means parity.

Meanwhile, in Syria, the situation has grown much more precarious. The end of US-Russian peace efforts has emboldened those forces seeking a military solution. The Russian military is probably gambling that the outgoing administration in Washington will not start a war against Damascus in what remains of the Obama presidency. Thus, defeating the rebels and what was Jabhat al-Nusra, al-Qaeda’s former franchise, in Aleppo is possible and, with it, a decisive turn in the Syrian war.

The gamble may or may not pay off. Should the rebel forces acquire the capability of shooting down Russian aircraft, the situation may change, as it did in Afghanistan in the 1980s. However, unlike in Afghanistan, retribution might follow soon. Syria, for most of 2016 the site of US-Russian collaboration, could easily turn into a battlefield between the two — with the proxies first taking aim at the principals, and the principals then shooting back not at the proxies, but at each other.

This is an exceptionally disturbing prospect that should keep people in Moscow and Washington awake at night. But the new highly asymmetrical relationship between the two powers leaves almost no room for mutual respect.

“Putin’s Russia” is increasingly treated in the western media the way America’s old adversaries were dealt with — from Slobodan Milosevic’s Yugoslavia to Saddam Hussein’s Iraq to Muammer Gaddafi’s Libya. As Boris Johnson, the UK foreign secretary, has put it, Russia is in danger of becoming a rogue state. Meanwhile, in eastern Europe there are cheers for US fighter aircraft taking on the Russians — and winning.

In such volatile times, it is best to remain calm and sober. No US-Russian co-operation on Syria, or on any other significant issue for that matter, can be expected during the final months of the Obama administration. The American president owes it to himself to make sure that a US-Russian collision does not happen on his watch. And Mr Putin must honour his pledge to avoid turning Syria into a new Afghanistan for Russia.

The US and Russian defence establishments, for all the sincerity of their mutual dislike, need to abide strictly by the rules that reduce the risks of incidents between their air forces operating in Syria — now officially on opposite sides.

Tragically, Syria’s civil war will go on unabated. So far, the Americans and the Russians have proved incapable of ending it. However, if they do not come to blows in the weeks and months ahead, they may eventually find themselves back in the negotiating room at some point. Moscow and Washington cannot make peace in Syria by themselves. But a settlement is impossible without them.

This op-ed was originally published in the Financial Times.