"We have charged our respective foreign ministers with starting consultations on this subject... but we can not yet say whether this will lead to an extension of START3," Putin told reporters after a G20 summit in Osaka on Saturday.

Putin did not say when talks would begin.

START3 refers to a proposed agreement between the two nuclear powers for which negotiations broke down years ago.

Intended as a successor to previous agreements, it would have required them to lower their numbers of deployed nuclear weapons.

The two countries are currently covered by the New START treaty signed in 2010, which caps the number of nuclear warheads well below Cold War limits.

But it expires in 2021 and Putin has been calling on the United States to negotiate an extension, saying Washington's failure to do so is a threat to arms control.

Together with another agreement known as the Intermediate-Range Nuclear Forces (INF) treaty, New START is considered a centrepiece of superpower arms control.

Earlier this month, Putin said Russia was prepared to drop New START if the US continues to put off negotiations, warning of a "global catastrophe" if Washington works to dismantle the international arms control regime.

Moscow suspended participation in the INF treaty in March after President Donald Trump's White House announced it would ditch the key agreement for alleged Russian violations of the terms.