"We must be at the disposal of our Japanese friends on the monetary side," the economy minister said after a cabinet meeting in Paris.

"I have called for a G7 meeting at the level of finance ministers and central bankers" to thrash out how best to offer financial support to Japan which has been rocked by a monster earthquake, tsunami and a damaged nuclear plant.

An aide said the meeting would take place via a telephone conference late Thursday.

Similar G20 talks are also expected although this has not been finalised, the source told AFP.

In Berlin Germany's Finance Minister Wolfgang Schaeuble told reporters that G20 discussions on Japan could take place on March 31 in Nanking, China during scheduled talks on the international monetary system.

Lagarde, calling for solidarity, described the situation in Japan "extremely worrying on the human, environmental and economic levels."

The head of a French nuclear safety agency said Wednesday that there was a "radioactive plume" coming from Japan's stricken Fukushima nuclear plant which was likely to expand in coming days.

France this year presides over the G20 group of the richest and top emerging nations.

The G7 includes Japan and France along with the United States, Britain, Germany, Canada and Italy.

US Treasury Secretary Timothy Geithner said Tuesday that Japan, the world's third largest economy, can handle looming reconstruction costs, despite the havoc caused by the quake, tsunami and failing nuclear facilities.