SAO PAULO, Brazil (AP) _ Well-heeled Brazilian farmers tilling rich soil on the fringes of the Amazon rain forest fear their holdings could be targeted in a land reform push by the Bolivian president, who just nationalized his nation's natural gas industry.

President Evo Morales has said his leftist government is eyeing large Brazilian-owned farms in Bolivia's eastern Santa Cruz province _ the country's wealthiest _ as it gears up to confiscate unproductive land and redistribute it to poor Bolivian farmers and Indians.

Under the land plan, holdings that aren't being actively used for farming or grazing could face confiscation. However, the plan is at an early stage and few people, if any, know how its rules will be defined, raising concern among large Brazilian farmers that even their productive holdings could be confiscated.

The government plans to redistribute 54,000 square miles of land _ an area roughly the size of Alabama _ mostly in Bolivia's vast eastern lowlands.

Speaking from Vienna, Austria, ahead of a summit of Latin American and European leaders, Morales said he respects Brazilian farmers operating in Bolivia, but that ``some Brazilian companies are illegally operating in our territory.''

While Morales didn't provide more details, Brazilians who have been farming in Bolivia for more than a decade were unsettled to learn they had been singled out even though they say they keep their land productive and provide jobs for Bolivians.

``The uncertainty is huge right now because we just don't know what's going to happen,'' Denis Barbieri, who employs 70 Bolivians and grows corn and soy on 13,600 acres in Santa Cruz, said in a telephone interview Thursday.

Brazilian farmer Roberto Zacarias, who has planted soy on his 10,000-acre farm since 1994, agrees that some large unused plots should be redistributed.

But he said he worries that Morales' agrarian reform will embolden organized groups of poor farm workers to invade productive land, and could put a halt to new investment in Bolivian agribusiness.

In the late 1980s, Brazilians first became attracted to Bolivia's undeveloped flat land, which has fertile soil, plentiful water and a tropical climate _ perfect for crops such as soy, corn, sunflowers, rice and wheat.

Zacarias said Brazilian farmers brought agricultural expertise to Bolivia, boosting employment and helping to turn soy into Bolivia's second-most important export product after natural gas.

``It was an attractive place to invest,'' he said. ``Now it's scary to invest here.''

Much of the land earmarked for redistribution was originally given away during the 1970s and early 1980s military dictatorships of President Hugo Banzer and President Luis Garcia Meza, presumably to people with close ties to their administrations.

Morales announced a state takeover of Bolivia's vast natural gas reserves on May 1.

His administration also is threatening to start enforcing a law preventing foreigners from owning land within 30 miles of its borders, a move that could mean the expulsion of thousands of poor Brazilian subsistence farmers who have lived for decades in Bolivian territory.

Brazil this week sent diplomats to the city of Cobija in the Bolivian province of Pando to protect the interests of Brazilians living in the area just across the border from the Brazilian Amazon states of Acre and Rondonia.

Bolivia's National Agrarian Reform Agency said it is investigating 250 land purchases by Brazilians in Bolivia, near the countries' border, to determine whether the land was legally obtained.

While the area in Pando province has become home to about 5,000 Brazilians in recent decades _ most of them eking out a living _ Bolivian politicians also claim Brazilian loggers have illegally bought up land.

In one case, a company run by a Brazilian and a Bolivian acquired a massive tract of 99,000 acres just four miles from the border, said Beimar Becerra, a member of Morales' Movement Toward Socialism party.

The company was given 15 days by government officials to prove that the two maintain legal residency in Bolivia, or stop operating altogether, according to the state news agency ABI.

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Associated Press writers Harold Olmos in Rio De Janeiro and Alexander V. Ragir in Sao Paulo contributed to this report.