Russia will pay special attention to building infrastructure for its nuclear forces in 2023, Defense Minister Sergei Shoigu said on Wednesday.

Shoigu said in televised comments that Russia would also work to improve the combat capabilities of its missile forces and that facilities were being built to accommodate new missile systems. Russia has the largest stockpile of nuclear weapons in the world, with close to 6,000 warheads.

President Vladimir Putin has placed territory seized by Russia in Ukraine under Moscow's nuclear umbrella, warning that he is ready to defend Russia's "territorial integrity" by all available means. The United States says it has warned Russia about the consequences of any use of nuclear weapons.

Russia and the United States were due to hold talks in Cairo this week on their existing New START treaty, which limits the number of warheads each can deploy.

But Moscow pulled out on the eve of the meeting, accusing the United States of toxic anti-Russian behavior and trying to manipulate the treaty to its advantage.