The new US nuclear weapons guidelines are a significant policy shift that show President Barack Obama is making good on his commitment to reduce atomic weapons, a leading defence think tank said Tuesday.

“I welcome the release of the Nuclear Posture Review and its core message: that the United States is taking steps to reduce the role of nuclear weapons in its overall national security policy,” the head of the Stockholm International Peace Research Institute (SIPRI), Bates Gill, said in a statement.

His comments came after the Obama administration released the long-awaited policy document on its nuclear strategy that sharply limited the scenarios in which the United States would use atomic weapons.

“By deciding not to pursue new nuclear weapons, the US will forego next-generation weapons and the expansion of missions which such new weapons might fill,” Gill said, lamenting nonetheless that the new nuclear policy “fell short of a ‘no first use’ declaration.”

Tuesday’s announcement, he said, “signals the most significant policy shift of any of the three Nuclear Posture Reviews since 1994 towards reductions in the role of nuclear weapons.”

“All in all, President Obama is making good on his commitment to work towards a world without nuclear weapons,” Gill said.

Obama and his Russian counterpart Dmitry Medvedev are set to sign a new disarmament treaty in Prague on Thursday, the first such pact in nearly a decade, after months of difficult negotiations.