The US and Russia officially extended the New Start nuclear arms control treaty on Wednesday, two days before it was set to lapse.
The treaty, which came into effect in 2011, requires both countries to keep their nuclear stockpiles to less than 1,550 warheads.
“The New Start treaty’s verification regime enables us to monitor Russian compliance and provides us with greater insight into Russia’s nuclear posture," US Secretary of State Antony Blinken said.
Mr Blinken said that was obtained "through data exchanges and on-site inspections that allow US inspectors to have eyes on Russian nuclear forces and facilities".
“The United States has assessed the Russian Federation to be in compliance with its New Start Treaty obligations every year since the treaty entered into force in 2011,” he said.
The 2011 treaty has a mechanism for extension without US congressional approval, and Russian President Vladimir Putin signed legislation extending the treaty last week.
Former US president Donald Trump had sought modifications to the treaty before agreeing to extend it.
The Trump administration wanted the treaty to limit Russia’s short-range nuclear weapons, which are not covered under the existing pact. Mr Putin rebuffed Mr Trump’s conditions.
But the Biden administration is pledging to build on the New Start treaty to address other arms control issues with Russia.
“President Biden has made it clear that the New Start treaty extension is only the beginning of our efforts to address 21st century security challenges,” Mr Blinken said.
“The United States will use the time provided by a five-year extension of the New Start treaty to pursue with the Russian Federation, in consultation with Congress and US allies and partners, arms control that addresses all of its nuclear weapons.
“We will also pursue arms control to reduce the dangers from China’s modern and growing nuclear arsenal.
"The United States is committed to effective arms control that enhances stability, transparency and predictability, while reducing the risks of costly, dangerous arms races.”