Tokyo: The US nuclear safety chief says he is comfortable with Japan's announcement that its tsunami-damaged nuclear power plant has reached stable conditions and is ready to enter a new phase leading to its eventual closure.

Gregory Jaczko, chairman of the US Nuclear Regulatory Commission, said Tuesday that significant progress has been made at the Fukushima Daiichi nuclear power plant since the March disaster.

He said measures taken by Japan have been consistent with how the US would handle a similar crisis.

Japan announced last Friday that the Fukushima plant had met "cold shutdown conditions," although experts have said the plant remains vulnerable and emits some radiation.

Jaczko promised continuing support for Japan's cleanup effort, which will be a decades-long project.