States Parties to the Treaty on the Prohibition of Nuclear Weapons in Vienna have stressed its significance amid growing nuclear threats from Russia, on Day 1 of their first progress meeting.

The three-day meeting of parties to the UN treaty opened on Tuesday.

Chair Alexander Kmentt of Austria said in the opening remarks that "all indicators for nuclear weapons are pointing in the wrong direction," expressing his worries about accelerating debates on nuclear deterrence and the rising threat of the use of such weapons.

The New Zealand delegate said Russian President Vladimir Putin's threat to use nuclear weapons has brought the world once more "to the brink of a nuclear catastrophe."

Kmentt said 33 non-members have expressed their intention to attend the meeting as observers, and some countries, including Germany and the Netherlands, will deliver speeches on Day 2.

The US, Russia, China and other nuclear-armed states have not joined the treaty. Neither have Japan and some other nations under a nuclear umbrella.