UPDATE 2-G20 to wait for US crop report before food price action

* Officials decided to wait for USDA data-French farm min

* Leaders could convene emergency meeting but tools limited

* No threat to world food security - farm min statement

* USDA monthly report due on Sept. 12

* French farm min calls for taxes to ease speculation (Adds French ministry statement)

By Sybille de La Hamaide

PARIS, Aug 28 (Reuters) - G20 nations taking stock of the third global food price surge in four years will wait for September's crop report from the U.S. Department of Agriculture before deciding whether to take joint action on the issue, France's farm minister said on Tuesday.

Senior officials held a conference call on Monday on rising prices after drought in the United states and poor crops from Russia and the Black Sea bread basket stirred new fears about food supply and inflation.

"There will be a communication at the end of September. I will wait for the results given by the United States around Sept. 12 on the latest estimates for corn supplies," French Agriculture and Food Minister Stephane Le Foll told BFM TV.

The decision to wait for the USDA report was taken at a conference call between senior officials of France, the United |States and G20 president Mexico on Monday. Representatives from the United Nation's Food and Agriculture Organisation (FAO), the World Bank, the OECD and the International Food and Policy Research Institute (IFPRI) were also on the call.

The call was organised in the framework of the Agricultural Market Information System (AMIS), created by the G20 last year.

France, which currently presides over the G20 agriculture body had initially said a decision would be based on an AMIS report also due in mid-September.

Officials in the call, held via video conference, discussed the drought in the United States that lead to a surge in corn and soybean prices and a drought in the former Soviet Union that slashed wheat crops, but they stressed that rice prices remained stable as opposed to 2008 when food price spikes triggered unrest in poorer countries, the ministry said.

"The current market situation is thus worrying," the French said in a statement, immediately adding however that "no threat is hanging over world food security."

The head of the FAO called the G20 on Monday for coordinated action to ease worries about food prices.

TAX FOOD PRICE SPECULATION

If G20 leaders decide the situation needed international intervention, France could trigger an emergency meeting of the so-called Rapid Response Forum created by the G20 last year to deal with surging world prices.

"Stephane Le Foll remains vigilant to any new element, mainly the next USDA report, that could justify a quick convocation of the Forum," the ministry said in the statement.

However, its main tool would be limited to talks to avoid unilateral trade restrictions by large producing countries that could lead to surge in prices, such as the one seen after Russia banned exports after a drought slashed its crops in 2010.

Le Foll also blamed speculation for the surge in prices and reiterated calls for taxes on financial transactions.

"There have been transfers, speculators leaving other markets to come to food markets. We need to stop this," he said on BFM TV.

"We need to tax financial transactions in any case," he said, also calling for position limits on derivative markets.

France had already called for similar moves when negotiating over G20 agriculture last year but G20 members had failed to reach an agreement.

At EU level, however, the executive has proposed a bloc-wide tax on financial transactions including stocks, bonds and derivatives from January 2014.

French President Francois Hollande was due to meet the head of the country's largest farm union FNSEA later on Tuesday. Top of the agenda will be the surge in farm commodities prices and tools to combat it, a spokeswoman said. (Reporting by Sybille de La Hamaide; editing by Veronica Brown and Keiron Henderson)