Britain's first new nuclear power plant in decades could be delayed amid reports an EDF board meeting to decide whether to invest in Hinkley Point Power Station has been postponed.
The French energy firm's board was expected to meet on Wednesday to finalise the decision.
But French paper Les Echos and environmental group Greenpeace said the decision had now been delayed reportedly due to funding difficulties.
EDF declined to comment on the reports.
In October, EDF agreed a deal under which China General Nuclear Power Corporation (CGN) would pay a third of the cost of the £18bn project in exchange for a 33.5% stake.
Analysis by John Moylan, BBC industry correspondent
Is the plan for Britain's first new nuclear plant in a generation in trouble?
What is clear is that EDF faces major financial challenges.
Its share price has halved in the past year as falling French power prices have hit earnings.
Its current nuclear build projects in Finland and at Flammenville are over-budget and delayed.
It's facing a costly refurbishment programme to extend the life of its French nuclear plants. And in Hinkley Point C, it would be committing to a project that will cost more than its current market capitalisation.
It also has to placate its unions, which fear the project could put the entire company at risk
But EDF has already ploughed £2bn into Hinkley. And with so much political capital invested by the French and British governments too, it would be astonishing if EDF was to fall at the final hurdle.
The final investment decision by EDF was expected to be a formality.
But Les Echos said the French firm was struggling to find the cash for its 66.5% stake and was now "putting pressure on the [French] state, which owns 84.5% of EDF, to come up with fresh funds".
It said a final investment decision would now be made at the earliest at EDF's annual results on 16 February.
The reports contradict recent statements from EDF chief executive Jean-Bernard Levy who said just a week ago that the "two nuclear reactors that EDF plans to build at Hinkley Point will be launched very soon".
Hinkley is due to start generating in 2025, and is expected to provide 7% of the UK's electricity once it is operational.
But the project was originally due to open in 2017, and it has come under fire for both its cost and delays to the timetable for building.
The government has also been criticised for guaranteeing a price of £92.50 per megawatt hour of electricity - more than twice the current cost - for the electricity Hinkley produces.
Greenpeace executive director John Sauven said: "The EDF board is clearly rattled as they delay yet again this crucial investment decision. It could well signal curtains for Hinkley.
"EDF managers as well as employee representatives on the board are deeply concerned this project is too risky and too expensive."
Meanwhile, the chief executive of Legal & General has described the project as "a £25bn waste of money".
Nigel Wilson told BBC 5 live: "The world is moving towards clean green and cheap energy."
"Solar, wind will play a much more important role. Hinkley is probably the most expensive energy we can think of right across Europe. That's really bad for society."