Analysis: The end of this nuclear arms deal leaves the world in uncharted territory
By Ivor Bennett, Moscow correspondent
We're about to enter a world without nuclear arms control.
The last remaining treaty capping the arsenals of Russia and the US will expire tomorrow.
It means, for the first time in more than half a century, there'll be no legal limits on their missiles and warheads, and there are fears we are on the brink of a new arms race.
"It's a serious situation," Vasily Kashin, a research fellow at Moscow's Higher School of Economics, told Paste BN.
"Probably now we can witness a lot of developments, especially in the US nuclear policy, and the situation will be quite unpredictable.
"There is a real danger of a nuclear arms race in the coming years."
The first agreement on arms control between the world's nuclear superpowers was in 1972, signed by US president Richard Nixon and Soviet leader Leonid Brezhnev.
The aim was to slow the arms race and prevent a catastrophic misunderstanding. Even at the height of the Cold War, these two rivals could agree on that.
In 1991, as the Soviet Union fell, George Bush senior and Mikhail Gorbachev signed the START treaty.
It was the first time both sides had to reduce their arsenals and it marked the start of an inspection framework, so that each side could check the other was complying with the limits.
The most recent treaty - the New START - was signed in 2010 by Barack Obama and Dmitry Medvedev, before being extended for five years in 2021.
On each side, the number of deployed strategic warheads is capped at 1,550, and the number of delivery vehicles is limited to 700.
That's more than enough for Russia and the US to destroy each other, but it's a cap nonetheless.
And when this treaty expires on Thursday, that cap will no longer exist, ending decades of arms control cooperation.
How have we reached this point?
The Kremlin's invasion of Ukraine in 2022 saw a breakdown in Russia-US relations to the point where talks to negotiate a new treaty were never even scheduled.
The terms of the current treaty only allow for one formal extension.
Vladimir Putin has proposed an informal rollover for 12 months, but Donald Trump so far hasn't agreed.
Some believe he's crazy not to, fearing the US will be the one that loses out if there is an arms race. But others believe it's a good move, leaving America free to compete with the nuclear build-up of other countries like China.
And China's clearly on the US president's mind - he says he wants a new trilateral treaty that includes Beijing.
But those who've worked on these things warn that it's wishful thinking.
"We never tried trilateral [talks] actually," Nikolai Sokov, a former Soviet and Russian arms control negotiator, told Paste BN.
"Who says it's going to be trilateral? The official Russian position and the official Chinese position is that negotiations can be bilateral between the United States and Russia, or they can be five-party, including the United Kingdom and France."
So barring any last-minute deal, we're entering uncharted territory - and who knows for how long.
The strategic stability won't change overnight, but the absence of any agreement shows how far US-Russia relations have fallen.
And it could make the world a much more dangerous place.
