The only remaining arms control treaty between the world’s largest nuclear powers – the New Start – is on shaky footing.

Russian President Vladimir Putin said his country was suspending its observation of the treaty, following complaints by United States President Joe Biden’s administration that Russia was refusing to allow inspectors into its territory.

Russia’s posture “threatens the viability of US-Russian nuclear arms control”, the State Department said in January.

Russia argues it would be inappropriate to allow inspections in its territory while the two countries are in a stand-off over Russia’s war in Ukraine.

1. What is the New Start?

Under the accord, the US and Russia have committed to reducing deployed nuclear warheads (capped at 1,550 for each country) and limiting the number of delivery platforms, such as intercontinental ballistic missiles, to 700 or fewer.

The agreement also allows each country to conduct on-site inspections of the other’s weaponry and requires the exchange of data and notification concerning arms and facilities covered under the agreement.

The US and Russia signed New Start – formally the New Strategic Arms Reduction Treaty – in 2010 to replace the 1991 Start treaty. It took effect on Feb 5, 2011, and received its most recent five-year extension in 2021, after Mr Biden’s predecessor, Mr Donald Trump, pushed unsuccessfully to renegotiate it.

2. Has the treaty worked?

Yes, it has. The US and Russia reduced their nuclear arsenals to the agreed-upon limit by the 2018 deadline set forth in the treaty.

The US had 1,420 deployed warheads and 659 deployed strategic delivery systems as at Sept 1, 2022, according to the State Department. Russia had 1,549 deployed warheads attributed to 540 deployed strategic launchers.

Combined, the two countries account for about 90 per cent of the world’s nuclear weapons.

3. Why did inspections come to a halt?

On-site nuclear inspections in Russia were initially suspended due to the Covid-19 pandemic. The US says Russia refused to restart them in August 2022 because of mounting tensions over the war in Ukraine.

An attempt to restart talks in Cairo in November failed after Russia decided to postpone them.

Russia’s Ambassador to the US, Mr Anatoly Antonov, said in early February that his country “remains committed to the goals of the New Start treaty” but considers it “unjustified, untimely and inappropriate to invite the US military to our strategic facilities” while the two nations are on opposite sides of the conflict in Ukraine.

On Feb 21, Mr Putin announced that Russia was suspending its participation in the treaty.

4. Why did Mr Trump want to renegotiate New Start?

His administration called the treaty “deeply flawed” in part because it addresses only strategic nuclear weapons – long-range ones that can be used to threaten the other country’s territory – and not shorter-range, so-called tactical weapons. Russia’s tactical arsenal is much greater than that of the US.

The Trump administration had hoped to force Russia to agree to a freeze in its overall number of nuclear warheads. Even some Biden aides are on record sharing concern that New Start does not apply to short- and medium-range nuclear weapons.

5. What is the status of other arms control agreements?

Mr Trump withdrew the US from the Intermediate-Range Nuclear Forces (INF) Treaty, which was signed in 1987 by US President Ronald Reagan and Soviet leader Mikhail Gorbachev, and the Open Skies Treaty, under which more than 30 nations granted one another access to airspace for the purpose of collecting information on military activities.

The Biden administration decided not to re-enter the Open Skies Treaty over concerns that Moscow was not taking steps to comply with the agreement. BLOOMBERG