US National Security Advisor Jake Sullivan says the United States is ready to engage in discussions with Russia and China without preconditions on managing nuclear risks.

Sullivan was speaking at an event of the Arms Control Association, a private think tank, in Washington on Friday.

Referring to Russia unilaterally suspending its participation in a key arms control pact in February, Sullivan said, "the cracks in our post-Cold War nuclear foundation are substantial and they are deep." The New START treaty capped the number of strategic nuclear warheads that could be deployed on each side.

Sullivan added the world was entering an era that demands new strategies to ensure the safety and security of people around the world from nuclear threats.

Amid China's expanding nuclear buildup, Sullivan also said the US does not need to increase its nuclear forces to outnumber the combined total of the competitors in order to successfully deter them.

He said that it was possible for the US to maintain deterrence by modernizing its nuclear forces and developing cutting-edge conventional weapons.

Sullivan also stressed the need for UK and France to join talks with the US, Russia and China on enhancing transparency of nuclear arms control.