Budgetmakers in the U.S. Senate have moved to halt U.S. participation in ITER, the huge international fusion experiment now under construction in Cadarache, France, that aims to demonstrate that nuclear fusion could be a viable source of energy. Although the details are not available, Senate sources confirm a report by Physics Today that the Senate's version of the budget for the Department of Energy (DOE) for fiscal year 2015, which begins 1 October, would provide just $75 million for the United States' part of the project. That would be half of what the White House had requested and just enough to wind down U.S. involvement in ITER.

But the fate of the U.S. ITER effort is hardly sealed. Appropriators in the House of Representatives released their version of the proposed DOE budget on 18 June and not only supported continued U.S. participation in ITER, but also proposed giving the project $225 million next year. The House total is $75 million more than what the White House had requested. Moreover, the Senate bill that would fund DOE—the so-called energy and water bill—hangs in limbo, thanks to the political battle over the Obama administration's plan to use Environmental Protection Agency (EPA) regulations to set new limits on carbon dioxide emissions from power plants, especially those that burn coal.

The Senate move should come as no surprise, as key members have been critical of ITER's massive cost overruns and mounting delays. When the United States signed on in 2006 to build 9% of ITER's parts and subsystems, the U.S. effort was expected to cost $1.1 billion and ITER was expected to start its key energy-producing runs in 2013. In April, DOE officials estimated that the cost of the U.S. share of the construction had risen to $3.9 billion and that those key runs would not start until 2033. And last month, the Government Accountability Office found that, thanks to the lack of a credible schedule for the project as a whole, even those estimates are not reliable. Given the situation, Senator Dianne Feinstein (D–CA), the chair of the Senate Appropriations Subcommittee on Energy and Water Development, warned at a 9 April subcommittee hearing that the U.S. program could be in jeopardy. "This may be an opportunity to experience the power of the purse," she said.

As the subcommittee followed through on that threat, even a senator from a state directly involved in the U.S. ITER project spoke in favor of ending it. U.S. ITER has its headquarters at Oak Ridge National Laboratory in Tennessee. Nevertheless, at a 17 June subcommittee meeting on the budget bill covering DOE, Senator Lamar Alexander (R–TN), the ranking member on the Energy and Water Subcommittee, said that ITER hasn’t shown the progress it should. "We’ve withdrawn funding for the program," he said, and "that saves taxpayers $75 million this year, and at least $3.9 billion, and potentially $6.5 billion, over the life of the project.”

To kill ITER, Senate appropriators will have to persuade the White House and their counterparts in the House to go along. That may be a tough sell, as the report that accompanies the House version of the energy and water bill says that ITER "remains the most practical U.S. investment in the fusion energy sciences." However, the House bill warns that lawmakers will have to reconsider that position if the international ITER organization does not implement a raft of management reforms specified last year by an external review panel.

Before negotiations between the Senate and House can begin, Senate appropriators must first get their version of the energy and water bill out of committee. The bill has been stalled by political wrangling over a proposed amendment by Senator Mitch McConnell (R–KY) which would eliminate funding for enforcing new EPA climate regulations unless the secretary of energy certified that they would not cost jobs or raise the price of electricity. Avoiding a politically tricky vote on the amendment, Democratic senators scotched a 19 June hearing and vote on the bill by the full Appropriations Committee.