One of the items in the small type of President Obama’s fiscal 2017 budget was the proposal to drop funding for the Savannah River plutonium mixed oxide recycling plant, designed for converting weapons-grade plutonium into fuel for commercial nuclear power plants. The project is years late and billions of dollars over budget.

In the budget, the Energy Department’s National Nuclear Security Administration said simply that it would “pursue a dilute and dispose approach as a faster, less expensive path to meeting the U.S. commitment to dispose of excess weapons grade plutonium.”

That proposal, however, has drawn fire from politicians from South Carolina, where about 1,200 jobs and about $300 million a year could be lost. Sens. Lindsay O. Graham (R) and Tim Scott (R) as well as Rep. Joe Wilson (R), whose district includes the Savannah River site, have criticized the plan.

State Attorney General Alan Wilson (R) has filed a lawsuit in federal district court to keep the plant alive, arguing that abandoning it would violate an arms control agreement in 2000 between the United States and Russia for disposing of 34 metric tons of weapons-grade plutonium. “The Department of Energy has continually shown disregard for its obligations,” he said in a statement. “The federal government is not free to flout the law. This behavior will not be tolerated.”

Now a group of some of the most prominent former diplomats and nonproliferation experts — alarmed by the cost and proliferation risks involved with the MOX process — have weighed in on the side of the Obama administration. In a letter to Energy Secretary Ernest Moniz sent Tuesday, the 13 experts said that the arms control agreement with Russia does not require the United States to use the MOX recycling plant to deal with the plutonium from decommissioned weapons.

“In fact, the agreement explicitly allows each side to change plutonium disposition methods and was already modified once in 2010 to allow Russia to pursue an alternative disposition approach to its own MOX program, which, like ours today, was judged to be too expensive to complete,” the group said. “As long as our government pursues a reasonable alternative to dispose of the surplus material, the agreement is not a barrier to doing so.”

The group also raised concerns about what it called the increasing possibility that rivalry between China, Japan and South Korea — and fears of North Korea’s pursuit of more advanced nuclear weapons — could prompt those countries to build similar MOX plutonium plants, which could make it easier later to produce plutonium suitable for additional weapons.

“There are increased political pressures to proceed with plutonium separation in Japan and China, and to gain U.S. consent for reprocessing in South Korea,” they wrote. “While the plans are to produce plutonium fuel for power reactors, the same plutonium could be used to produce thousands of warheads.”

Japan is nearing completion of a costly plutonium recycling plant at Rokkasho, although it has pushed back the start date of the plant. And in South Korea, the letter notes, “shortly after North Korea’s latest nuclear-weapon test, both South Korea’s ruling party parliamentary floor leader and the party’s chief policy maker publicly urged that South Korea pursue nuclear reprocessing as a military hedge.” China is also seeking reprocessing technology from France.

The signatories to the letter include former ambassador Thomas Pickering; Jessica Mathews, a former head of the Carnegie Endowment for International Peace; former senior nonproliferation officials Robert Einhorn and Gary Samore; Ambassador Robert Gallucci, a former assistant secretary of State for political-military affairs; Joseph Nye, a former chairman of the National Intelligence Council; Ploughshares Fund President Joseph Cirincione; former Nuclear Regulatory Commissioners Peter Bradford and Victor Gilinsky; David Freeman, a former chairman of the Tennessee Valley Authority’s board of directors; Henry Sokolski, a former Pentagon official for nonproliferation; and Frank von Hippel, a former assistant director for national security at the White House’s Office of Science and Technology Policy.

Last year the group wrote to Moniz urging him and the Obama administration to end funding of the Savannah River site.

“If we fail to terminate our MOX program, we will have far less credibility to engage them in efforts to restrain such activities in East Asia,” the group’s letter concluded. “In short, contrary to the claims of its defenders, the arms-control and nuclear security arguments weigh heavily for ending the MOX project, not for continuing it.”