The head of the US Nuclear Regulatory Commission announced his resignation Monday, just months after a public spat with colleagues over the need for proof of safety in the wake of Japan's disaster.

Gregory Jackzo said that after three years in the post, it was "the appropriate time" for him to fight for public safety in a different forum.

In February Jaczko was the sole commissioner to oppose the approval of the first new US reactors in decades.

He argued for "binding commitments" from business that would address shortcomings highlighted by last year's Fukushima meltdown.

"I cannot support issuing this license as if Fukushima has never happened... In my view that is what we are doing," he said at the time.

Regardless, commissioners voted 4-1 to approve the construction of two 1,100 megawatt Westinghouse-Toshiba reactors at a facility in Vogtle, Georgia.

On Monday, Jackzo said: "This is the right time to pass along the public safety torch to a new chairman who will keep a strong focus on carrying out the vital mission of the Nuclear Regulatory Commission."

Jackzo said he will step down once his successor is confirmed.

Commenting on the announcement, the White House praised Jaczko's "efforts to further the mission" of the agency and said it intended "to nominate a new chairman soon."

It is unclear whether Jackzo will leave before his term is up next year.

Congressional deadlock makes the confirmation of a new chief commissioner highly unlikely before November's presidential elections.

There was little sign of that deadlock being broken on Monday.

Democratic Senator Barbara Boxer thanked Jaczko "for always fighting for the health and safety of the American people."

Republican Senator Mitch McConnell criticized his "troubling behavior as chairman," while claiming that he had "intimidated female workers."