By Ana Mano and Karl Plume

SAO PAULO/CHICAGO, Feb 12 (Reuters) - Harvesting delays inBrazil, the world's top soybean producer, are prompting buyersled by China to rely on rival exporter the United States forlonger than usual in 2021, according to government data andtraders.

Sustained demand for U.S. soybeans is accelerating anhistoric drawdown of U.S. supplies of the oilseed and couldfurther drive up soybean prices at a time of rising foodinflation as countries hoard staples during the pandemic.

Concerns over tight global soybean supplies after Chinadramatically increased purchases in recent months ignited a 4.5%U.S. soybean futures rally last month to a 6-1/2-year high.

Brazil usually harvests its soybeans in the first threemonths of the year, marking an end to the dominance of U.S.exports. However, that process has been delayed by a droughtlast year that slowed plantings, and rainfall at harvest time.

The country's shipments of soybeans in January were 28 timeslower than a year before at 49,500 tonnes, an amountinsufficient to fill up a single vessel, Brazilian trade datashowed.

In contrast, the United States, its biggest rival in globalmarkets, inspected some 8.9 million tonnes for shipment in themonth, the highest on record, according to United StatesDepartment of Agriculture (USDA) data.

Anec, a Brazilian group representing grain exporters likeCargill and Bunge, confirmed current shortagesin Brazil may give competitors an edge.

"We assume this is happening," Anec director Sergio Mendessaid by telephone, adding Brazil's low soy availability iselongating the U.S. export window.

In February Brazilian soy shipments could be as little as 6million tonnes, down from 8.5 million tonnes initially expected,Anec has said.

Brazil's supplies are only expected to normalize by March,one large trader told Reuters.

That could spell chaos at Brazilian ports, as by March andApril soybeans will be competing with sugar for finite loadingcapacity.

Speaking on condition of anonymity, the trader said it istapping grain suppliers in the United States and Argentina. Muchof the burden will fall on the United States, as Argentina's soyharvest does not start until March.

Importing countries, particularly China, have been boostingpurchases of grains and oilseeds during the pandemic to guardagainst shipping disruptions or further price increases inagricultural commodities.

China buys grains and oilseeds from South and North Americato make livestock feed. It is currently rebuilding its hog herdafter a deadly pig disease killed millions of animals.