Terrorists are avowedly trying to build nuclear bombs, but U.S. spending to safeguard the world’s atomic materials has dipped in recent years — and President Donald Trump plans to keep it that way, according to budget documents, independent experts and lawmakers.

An Energy-Water spending bill passed last week by the Senate in a package with two other spending measures proposes a slight increase for nuclear security programs. But it would still leave the budget for those efforts far below what it was just a few years ago.

“Nuclear terrorism remains among the most significant threats to the security of the United States, allies and partners,” declared the Trump administration’s nuclear posture review, released in February.

However, according to the Arms Control Association, Trump’s fiscal 2019 budget request for what the group calls “core” nuclear nonproliferation programs at the Energy Department is fully 18 percent lower than the level of funding such programs had eight years ago, even before accounting for inflation’s shrinking effect on purchasing power.

Moreover, Trump’s five-year Energy Department budget plan for fiscal years 2019 through 2023 would increase spending on nuclear security programs at an average of less than 1.5 percent a year, which is probably not enough to even keep pace with inflation.