The end! Moscow and Washington no longer have any boundaries

Guterres added that this is “a grave moment for international peace and security.”

The last nuclear agreement between the two powers, the New START treaty, expired on Thursday, formally freeing both Moscow and Washington from a number of limits on their nuclear arsenals and sparking fears of a global arms race, The Guardian reports.

“For the first time in more than half a century, we are facing a world without any binding limits on the strategic nuclear arsenals of the two states that possess the vast majority of the world’s nuclear weapons,” Guterres said.

He noted that New START and other arms control agreements have dramatically improved the security of all peoples.

“This dismantling of decades of achievements could not have come at a worse time. The risk of the use of nuclear weapons is at its highest in several decades,” he stated.

Guterres urged Washington and Moscow “to return to the negotiating table without delay and agree on a successor framework.”

The agreement, signed in Prague in 2010 by then U.S. and Russian presidents Barack Obama and Dmitry Medvedev, limited each side’s nuclear arsenal to 1,550 deployed strategic warheads, a reduction of nearly 30 percent compared with the previous limit set in 2002.

Russia and the United States control more than 80 percent of the world’s nuclear warheads.