Why does Russia want to revoke its ratification and how significant is it?
Earlier this month, Russian President Vladimir Putin said Russia should withdraw its ratification to "mirror" the position of the United States, but that he wasn't not ready "to say whether we should conduct nuclear tests or not."
Russia has nearly 6,000 nuclear warheads — the largest stockpile in the world.
Some experts see Russia's move as mostly symbolic as it doesn't appear to have immediate plans to resume nuclear testing. Nikolai Sotov, a Russian nuclear expert and senior fellow at the Vienna Centre for Disarmament and Non-Proliferation, says he believes the country is trying to make a political statement at a time of increasing hostilities with the West.
"This really illustrates (Russia's) tough approach," he said in an interview with CBC News. "Moscow used to be afraid of not having constructive negotiations, and now they are not afraid."
Russia has said it would remain a signatory to the CTBT, and continue to supply data to the global monitoring system.
WATCH | Why Russia-North Korea arms deal is 'a match made in hell':
Two of the world's most isolated leaders, Vladimir Putin and Kim Jong-un, met to discuss a potential arms deal. Andrew Chang breaks down what each leader wants and why some analysts say the meeting is "a match made in hell."
Lynn Rusten, vice-president of the Global Nuclear Policy Program at the Washington, D.C.-based Nuclear Threat Initiative, says even if it is a political manoeuvre, it can still be viewed as an implicit threat by Russia.
"You can also view it as another manifestation of Russia's kind of nuclear coercion in this Ukraine crisis," she told CBC News.
She says if Russia were to resume testing, it would put pressure on other countries to start testing nuclear weapons.
"The treaty's already under tremendous strain because the non-nuclear weapons states see that the nuclear weapon states … are going in the wrong direction in terms of starting to increase their nuclear arsenals."
Why has the U.S. not ratified it?
The U.S. signed the treaty in 1996, but the Senate voted against ratifying it in 1999.
At the time, U.S. officials expressed concern that the country might not be able to evaluate the reliability of its stockpile of weapons without the ability to occasionally do nuclear tests. Another concern was whether there was a strong enough system in place to ensure countries adhered to the treaty.
Rusten says those concerns have now mostly vanished because of the monitoring systems now in place, but she says there hasn't been a strong desire to ratify it in the U.S.
"There's kind of an ideological antipathy toward arms control in some quarters," she said.
Even though the U.S. hasn't ratified it, she says it has been committed to the moratorium on any nuclear testing.
What is the status of global nuclear disarmament?
Throughout Russia's war on Ukraine, Putin and other Russian officials have made nuclear threats.
Earlier this year, Russia announced it was suspending the New Start Treaty with the U.S., which is the last remaining arms treaty between the two countries. It limits the number of strategic nuclear warheads on both sides.
Of the 12,500 nuclear warheads in existence, nearly 90 per cent belong to the United States and to Russia, according to the Federation of American Scientists. In March, Russia announced it was deploying tactical nuclear weapons to Belarus