There are reports in Japan that Hitachi is considering scrapping its £12bn Wylfa Newydd nuclear power plant plans.
TV Asahi reports that there is concern about projections of further increases in construction costs, with the Horizon project due to be discussed at a board meeting on Tuesday.
Hitachi said it would not comment "on rumours or speculation".
Around 9,000 workers would be involved in building two nuclear reactors on Anglesey, if they get the go ahead.
It would aim to have a generating capacity of 2900 MW by the mid 2020s and have a 60-year operational life.
The original Wylfa nuclear plant near Cemaes closed in 2015 after more than 40 years service.
A Hitachi-Horizon spokesperson said since June it had been in formal negotiations with the UK Government regarding financing of the Wylfa Newydd project "in a way that works both for investors and the UK electricity customer".
Any potential funding agreement with the UK and Japanese governments are likely to mean they take a stake in the Hitachi project in return for investment.
Work has already begun at the site although Horizon Nuclear Power, which is owned by Hitachi, still needs to get planning permission and marine licences.
It is unclear how much this latest development is Hitachi raising real concerns about its commitment to Wylfa Newydd or whether it is an attempt by the company to get a better deal from the UK and Japanese governments.
"This is one of the aspects of the project development phase that must be concluded before construction of Wylfa Newydd can go ahead, but the discussions are commercially confidential," said Hitachi-Horizon officials.