The nuclear arsenals of the United States and Russia continue to fluctuate as the two countries work to meet the terms of the New Strategic Arms Reduction Treaty (New START), according to the latest aggregate data Monday from the U.S. State Department.

The 2010 bilateral accord requires each country by next February to cap its nuclear arsenal at 700 deployed ICBMs, submarine-launched ballistic missiles, and heavy bombers; 1,550 fielded strategic warheads; and 800 deployed and nondeployed long-range launchers.

A nuclear detonation. Photo: U.S. Energy Department
A nuclear detonation. Photo: U.S. Energy Department

The April 1 numbers, containing data declared as of March 1, say that since the last numbers were released – with data declared as of September 2016 – the U.S. has reduced its deployed ICBMs, SLBMs, and heavy bombers from 681 to 673; Russia has increased its number from 508 to 523.

During that time the U.S. increased its deployed strategic warheads from 1,367 to 1,411; Russia decreased its own from 1,796 to 1,765. Meanwhile, the U.S. cut back its count of deployed and nondeployed long-range delivery systems from 848 to 820, while Russia did so from 847 to 816.

Some fluctuation in each side’s numbers is expected and generally not considered problematic for strategic stability between the two nations. Hans Kristensen, director of the Nuclear Information Project for the Federation of American Scientists, has previously said that fluctuations are temporary as the two countries carry out their nuclear modernization programs.