By Benjamin Mallet and Forrest Crellin

PARIS (Reuters) -French power giant EDF doesn't expect to make a final decision on building six new nuclear reactors in the country until the second half of 2026, CEO Luc Remont said on Friday, after auditors flagged uncertainties over financing and design.

French President Emmanuel Macron announced a plan in 2022 for the state-owned utility to build six new reactors to rejuvenate its ageing nuclear fleet, with construction due to start in 2027.

EDF, which runs Europe's largest nuclear fleet, had said last year it would take a final investment decision (FID) at the end of 2025 or early 2026. Costs were estimated in 2023 at 67 billion euros ($70.12 billion).

Last month the French court of auditors recommended that the company should not take a final investment decision until it finalises its designs and secures financing.

Speaking to reporters on Friday as EDF announced annual results, Remont said a decision was now expected "around the second half of 2026".

EDF's core profit fell last year to 36.5 billion euros ($38.28 billion), down from 39.9 billion euros a year earlier, it said on Friday, hit by lower power prices.

With more renewable power reaching the grid and power demand low, the number of hours with market prices below 10 euros per megawatt hours almost tripled compared to 2023, it said.

A reduction of another 7-9 billion euros in EBITDA is expected this year, said Remont.

Low prices will challenge EDF, said Nicolas Goldberg, partner at Paris-based Columbus Consulting.

"If EDF can't wipe out its debt this year with profits, it can be concerning because it would mean the debt from their maintenance work is persistent and would reduce the group's ability to finance their investments through debt," he said.

The company said 2024 net debt was stable at 54.3 billion euros.

EDF's net profit rose to 11.4 billion euros, compared to 10 billion in 2023 thanks to a significant reduction in impairment charges on Britain's long-delayed Hinkley Point C project.

Remont said the company continues to seek new investors in the project after Chinese partner CGN pulled out.

EDF also took a 900 million euro impairment charge on the Atlantic Shores offshore wind farm project in the United States "to reflect the new American political landscape", said Remont.

Partner Shell has already written down its stake in the venture.

($1 = 0.9555 euros)

(Reporting by Benjamin Mallet and Forrest Crellin. Writing by Dominique PattonEditing by David Goodman, Tomasz Janowski and Elaine Hardcastle)