The world’s biggest science experiment may get more time and money for completion when nuclear officials convene on Wednesday in France.

Supervisors of the International Thermonuclear Experimental Reactor, or ITER, are gathering for a two-day meeting in southern France to discuss whether to accept a revised timeline and budget, spokesman Laban Coblentz said by telephone. ITER Director General Bernard Bigot said in April that the 500-megawatt fusion reactor may need another five years and 4.6 billion euros ($5.2 billion) before it begins testing.

ITER has become the make-or-break demonstration project that will help determine whether nuclear fusion has a future as a source of energy and electricity. Unlike traditional nuclear plants, where atoms are broken apart, fusion makes energy by smashing atoms together at high speeds so that they merge into plasma burning hotter than the sun.

Scientists working on the ITER are trying to create 500 megawatts of power from plasma burning at 170 million degrees Celsius (338 million degrees Fahrenheit). The project would use only 50 megawatts of energy to cool and contain the reaction, proving the technology is a possible source of electricity and heat.

While fusion is decades away from deployment on any commercially viable project, it has a remained a well-funded goal since Soviet scientists tested the first tokamak reactor in 1956. The ITER reactor follows that design. Should it work, commercial fusion plants might coming online sometime after 2050.

ITER’s cost estimates have doubled to at least 20 billion euros since the project was approved in 2006. Construction began in 2013 in Cadarache, France, after decades of negotiation and planning among the consortium members: the U.S., China, the European Union, India, Japan, Russia and South Korea. The recurring delays and cost overruns have risked undermining fusion’s potential as a low-carbon-emitting power source to avert global warming.