UPDATE 1-Mosaic reviewing Russian potash exports

(Adds background, updates share price moves)

NEW YORK, Oct 26 (Reuters) - Fertilizer maker Mosaic Corp (MOS.N) said on Friday it is reviewing its position following news of a sinkhole problem that threatens to disrupt all potash shipments from Silvinit, a major Russian potash producer.

The sinkhole from a flooded potash mine could halt shipments from Silvinit, which accounts for about 10 percent of world supply.

"We're reviewing the sinkhole situation," said Douglas Hoadley, a spokesman for Mosaic.

"The potash situation was already very tight. We had stopped sales (two weeks ago) because we were already sold out through December," he added.

"We had announced a price increase and we were trying to put together a program on new sales and it's all on hold right now while we examine the situation," said Hoadley.

Potash Corp of Saskatchewan (POT.TO) (POT.N), the world's largest producer of potash, announced on Thursday it had suspended new potash sales. Agrium Inc (AGU.TO), the smallest North American producer of the nutrient, earlier Friday announced that it was taking the same action.

Potash Corp, Mosaic and Agrium together own Canpotex, a marketing and distribution company which is also the world's largest exporter of potash. Most potash exports from the three companies' Canadian operations is sold through Canpotex.

Belarussian Potash Co, the Russian equivalent of Canpotex, will also suspend new sales contracts, Russia's Uralkali (URKA.RTS) said.

Uralkali and Belaruskali each own a 50 percent stake in Belarussian Potash Co.

Canpotex and Belarussian together control about two thirds of the world's potash exports.

Shares of Mosaic were up 4.6 percent in afternoon trade on the New York Stock Exchange, while Agrium was up 3.1 percent and Potash Corp was up 1.8 percent. (Reporting by Euan Rocha)