A U.S. military aide, carrying the "football" containing the launch codes for U.S. nuclear weapons, walks from Air Force One between U.S.Trade Representative Robert Lighthizer (L) and National Security Adviser John Bolton (R) as U.S. President Donald Trump arrives to attend the nearby G7 Summit in Charlevoix after landing aboard Air Force One at Canadian Forces Base Bagotville in La Baie, Quebec, Canada, June 8, 2018. (REUTERS Photo)

UNITED NATIONS, Sept. 26 (Xinhua) -- UN Secretary-General Antonio Guterres on Wednesday called for efforts toward a world free of nuclear weapons.

As the only weapons with potentially existential consequences, nuclear weapons pose a grave threat to international, national and human security. The only sure way to eliminate the threat posed by nuclear weapons is to eliminate the weapons themselves, he said.

However, the global security environment has deteriorated, making progress in nuclear disarmament more difficult yet also more important, he told a high-level plenary meeting of the UN General Assembly to commemorate the International Day for the Total Elimination of Nuclear Weapons.

Guterres asked for leadership from states possessing nuclear weapons.

The United States and Russia -- by far the largest possessors of nuclear weapons -- have made enormous progress in the reduction of their nuclear arsenals, he said. "I appeal to both governments to re-engage in the dialogue necessary to maintain their historic track record of bilateral arsenal reductions."

As a first step, the two countries should move to extend the New START Treaty (Strategic Arms Reduction Treaty) by the five years allowed for in its articles and commence discussions that could lead to further agreements on reductions, he said.

The two countries should also work together to overcome their dispute on the Intermediate Nuclear Forces Treaty, he said.

In addition, it is equally important that all states possessing nuclear weapons reinforce the norm against nuclear use, said the UN chief.

He asked those states to publicly recommit to the fact that a nuclear war cannot be won and therefore must never be fought; to refrain from developing new and destabilizing nuclear weapons; and to work immediately to fully implement all commitments undertaken on nuclear disarmament, especially under the Nuclear Non-Proliferation Treaty.

At the same time, all states have responsibilities in the pursuit of nuclear disarmament, he said.

Non-proliferation is central to the maintenance of international peace and security, and also essential for preserving an environment that is conducive to disarmament. Disarmament remains essential for sustaining nonproliferation. They are two sides of the same coin. Backward movement on one will inevitably lead to backward movement on the other, said Guterres.

All states should also work with nuclear-weapon states to bridge divides and seek a return to a common path toward the elimination of nuclear weapons, he said.

The time has come to make tangible progress to rid our world of nuclear weapons, he said.