Defense Secretary Jim Mattis takes part in a news conference at the Pentagon on May 19. (Shawn Thew/European Pressphoto Agency)

Defense Secretary Jim Mattis has decided to cancel a plan to end the U.S. military’s use of most cluster munitions after 2018. The change paves the way for the Pentagon to resume purchasing cluster bombs and ensures the weapons will remain part of U.S. arsenals and planning for years to come.

The policy change, which reverses a 2008 decision by the George W. Bush administration, is sure to provoke opposition from lawmakers and arms-control organizations, who say the weapons indiscriminately kill civilians caught in war zones and who argue that the United States is out of step with the rest of the world on the issue.

“The Department of Defense has determined that cluster munitions remain a vital military capability in the tougher warfighting environment ahead of us, while still a relatively safe one,” Pentagon spokesman Tom Crosson told me. “This was a hard choice, not one the department made lightly,”

The Pentagon’s senior leadership determined that ending the use of cluster munitions currently in U.S. stocks would create a capability gap for U.S. forces, adding risk in a conflict and weakening deterrence, Crosson said. But he added that the new policy includes a commitment to acquiring safer and more reliable cluster munitions, which was one goal of the Bush administration policy.

The United States is not a party to the 2008 Convention on Cluster Munitions, which bans all use, purchase or transfer of the weapons. The pact includes 102 nations as full parties and 17 as signatories. But the U.S. military has not used cluster bombs in large amounts since 2003, at the start of the Iraq War. There is some evidence limited use occurred in 2009 in Yemen.

The Defense Department is expected to announce the new policy Friday, but it has been briefing lawmakers ahead of the announcement. The 2008 policy would have banned the use of all cluster munitions that have an unexploded ordnance rate above 1 percent. Going forward, the U.S. military will be allowed to buy cluster bombs that don’t meet that standard, so long as they have “advanced safety features” such as self-destruct mechanisms that would kick in after they are dropped.

The Defense Department will also slow its ongoing program to decommission the current U.S. stockpile of cluster munitions until the current stockpiles can be replenished with newer, safer weapons. No cluster  munitions have been purchased for the U.S. military since 2007.

In 2015 and then again this April, Sens. Dianne Feinstein (D-Calif.) and Patrick J. Leahy (D-Vt.) introduced the Cluster Munitions Civilian Protection Act, which if passed would have codified the 2008 Pentagon policy, banned funding for any cluster munitions that didn’t meet the 1 percent standard and called on the U.S. government to accede to the Convention on Cluster Munitions.

“A decade ago, the Pentagon announced that by 2018 it would no longer use cluster munitions with a failure rate exceeding one percent. On the eve of that deadline, the Pentagon has decided to go back on its commitment, just as it did after pledging to develop alternatives to antipersonnel landmines more than two decades ago,” Leahy said in a statement. “In these cases the Pentagon not only can’t be relied on to keep its commitment; it is perpetuating the use of an indiscriminate weapon that has been shown to have high failure rates, with devastating consequences for civilians.”

Under pressure from Congress and human rights groups, in 2016 the Obama administration stopped transferring cluster munitions to Saudi Arabia, which has reportedly used them in the war in Yemen.

Daryl Kimball, executive director of the Arms Control Association, said that U.S. policy on cluster munitions is already out of step with the vast majority of the world’s nations and that both the George W. Bush and Barack Obama administrations were working toward reducing stockpiles and eliminating their use.

“Reversing current U.S. policy in a way that resumes the use of even more dangerous types of cluster munitions, which the past two administrations decided were unnecessary, would be self-defeating and harmful to U.S. interests and to civilians caught in the middle of war zones,” he said.