* Grains prices squeezed higher by drought-hit supplies
* Argentina the world's No. 2 corn, No. 3 soybean exporter
* Sunny Pampas weather bolsters output hopes
BUENOS AIRES, Nov 5 (Reuters) - Farmers in grains powerhouse Argentina have jump-started corn and soy planting in recent days, bolstering harvest expectations thanks to a sunny streak that has improved conditions after months of flooding.
``Planting has begun again, except for the lowest lying areas that are still too soggy,'' said Tomas Parenti, an agronomist at the Rosario grains exchange.
This is good news for consumer nations that are counting on Argentina - the world's No. 2 corn exporter and No. 3 soybean supplier - to help replenish food stocks depleted by dry crop weather in Russia, the United States and Australia.
Argentine growers hope to step in with ample harvests despite the violent rainstorms that started in August and turned prime Pampas farmlands into unplantable mush. Delays in seeding have already prompted some analysts to cut output projections.
Now it looks as though the weather may give Pampas soy and corn another chance. Sun over the last two weeks in northern Buenos Aires, Santa Fe, Entre Rios and Cordoba provinces has firmed topsoils enough to allow seeding machines get back to work.
``Growers are advancing significantly with corn and soy planting,'' said German Heinzenknecht, a meteorologist at consultant Clima Campo.
``We'll be OK in the central farm belt at least until Thursday, when new showers will arrive from the south,'' he added. ``Southern Buenos Aires could get hit hard but rainfall in northern Buenos Aires and the rest of the central farm belt should not be excessive.''
The U.S. Department of Agriculture expects Argentina to harvest 55 million tonnes of soy and 28 million tonnes of corn in the 2012/13 crop year. But analysts had already started warning of losses - estimated at 20 percent for corn and 10 percent for soy - related to planting delays caused by floods.
The unusually wet weather has affected 190 million hectares (about 469 million acres) of wheat area, Parenti said.
About 3.7 million hectares of wheat were planted in Argentina this season and the Rosario exchange expects 2012/13 output of 10 million tonnes, down from 13 million tonnes last season.
This year's wheat planting was also reduced by farmers shifting to other crops to avoid export curbs that the government slaps on wheat and corn.
As 2012/13 corn and soy are still being planted, Parenti said it was too early to project flood-related losses for those crops.
Supply from Argentina is of key interest to exporters such as Bunge Ltd and Noble Group Ltd that operate huge grains terminals along the Parana River, which offers access to the busy shipping lanes of the South Atlantic.
The United Nations predicts world food demand will double by 2050, and South America is expected to provide most of the increase in grain production between now and then.
Shortages caused by bad U.S., Russian and Australian crop weather have squeezed Chicago soybean prices 26 percent higher this year. Corn prices are up 13 percent and wheat 29 percent.
Argentine farmers have planted 40 percent of the 3.4 million hectares estimated for commercial-use corn this season, lagging last year's tempo by 16.8 percentage points, the Buenos Aires Grains Exchange said late last week.
Some 3.6 percent of the 19.7 million hectares expected to be dedicated to soybeans in the 2012/13 crop year have been seeded, lagging 2011/12 by 9 percentage points, the exchange said.