EDF abandoned plans to bid for Constellation Energy (NYSE: CEG - News) in an attempt to wrest the US utility away from current acquirer Warren Buffett, blaming its decision to walk away on the rough credit markets.

The move deals a severe blow to the French nuclear operator's ambitions in the US, which could potentially be the world's most lucrative civil nuclear market.

Constellation, a Baltimore-based power company that controls three nuclear facilities, agreed to a $4.7bn takeover by Mr Buffett's Mid-American Energy last month after a crisis of confidence over its liquidity sank its shares and threatened its credit ratings.

Constellation quickly committed to Mr Buffett in spite of at least two other takeover offers, including one from EDF that was 33 per cent richer.

EDF, as it evaluated a new joint bid with US private equity firm KKR, had aimed to make an offer ahead of an upcoming Constellation shareholder meeting, in the hope that Mr Buffett's proposal would be voted down.

The French group's decision to scrap its bid now throws the future of Unistar - EDF's joint venture to build four reactors with Constellation - into question.

As it weighed a bid for Constellation in its entirety, EDF had also been considering whether instead to try to buy Constellation's half-stake in Unistar to take control of the venture. People close to the company said it had not ruled out that possibility.

US regulators prohibit majority foreign ownership of nuclear assets, which means EDF could have to sell that stake to a different US partner.

EDF may now have to strike deals with several US partners to reach its target of building at least four US nuclear reactors - a task that could prove more complicated.

The group, which runs France's 58 nuclear reactors, has been approached by several US utilities interested in domestic ventures, people close to the company have said.

EDF's board of directors had been on standby for a potential meeting last Friday or early this week, at which they had hoped to vote on a joint bid with KKR.

But last week's severe losses by global equities markets, combined with the difficult financing environment, convinced EDF's board that it was not prudent to take on additional acquisition risk atop its £12.5bn ($21.4bn) deal to buy British Energy, the UK nuclear operator.

EDF is already raising £11bn in debt to fund that deal and the additional financing it would need to execute a takeover of Constellation could be prohibitively expensive.