* More detail to emerge in coming days - RWE spokeswoman
* Hitachi has made an offer for Horizon - spokesman
* E.ON declines to comment
FRANKFURT/TOKYO, Oct 25 (Reuters) - RWE, Germany's No.2 utility, is in advanced talks to sell Horizon, its British nuclear joint venture with E.ON, a deal that analysts say could fetch up to 500 million euros ($648 million).
"We will be able to give more details in the coming days," a spokeswoman for RWE said on Thursday.
E.ON and RWE, under pressure from Germany's decision to phase out nuclear power, in March announced the sale of Horizon, a joint venture through which they had planned to invest 15 billion pounds ($24 billion) building plants in Oldbury and Wylfa with combined capacity of at least 6 gigawatts (GW).
German newspaper Sueddeutsche Zeitung reported that a consortium led by Japanese engineer Hitachi was the frontrunner for Horizon.
"Our interest in Horizon led us to bid (for the project), but since nothing has been decided, we cannot say anything further at this time," a spokesman for Hitachi said.
E.ON declined to comment.
Earlier this month, an industry source told Reuters that Westinghouse and its parent company Toshiba had submitted a bid for the joint venture, while Hitachi and Canadian counterparty SNC-Lavalin also made an offer.
The British government plans huge growth in its nuclear industry, with new power stations expected to come on line by 2025 to replace ageing plants.