Thousands of people have streamed out of this coca-growing region of central Bolivia, fearful that after U.S. troops finish assisting Bolivian police in the elimination of cocaine-processing laboratories in the northeast flat land, they will come here to uproot the coca crop.

U.S. and Bolivian authorities say their joint policing operation in the Beni region will not spread to the coca plantations to the west in the Chapare. They also deny another rumor that has alarmed peasants: that the Americans had brought with them deadly herbicides to use in coca eradication.

Public anxiety about what the Americans may do next is running as high as the Andes. While the poor farmers living here in wooden shacks are unlikely to run far, coca's profiteers -- the paste makers, the buyers, the prostitutes -- have fled the area, exiting in bus loads soon after U.S. troops landed in Bolivia 12 days ago.

As U.S. and Bolivian officials had hoped, the price of the coca leaf has dropped in the past week due to slackened demand. From 60 to 70 cents per pound before the Americans landed, the going rate for leaf here has fallen to 25 to 30 cents.

If the price can be kept down, the government expects to have an easier time persuading local growers to switch from coca to citrus fruits, bananas, rice and other crops that currently earn much less..

It is still possible to drive along the eroded two-lane road that traverses this forested region at the eastern base of the mountains and see thousands of picked coca leaves drying in the sun, spread on the ground in front of peasant huts. The tiny leaves, chewed by Indians for centuries to dull the pain of hunger, cold and illness, continue to be sold in markets, although more discreetly now, say local authorities.

In contrast, coca paste which is purified into cocaine, appears to have vanished. Police at road checkpoints say they have not found any of the paste they usually uncover during searches of passing vehicles. Their guess is that if the paste is still being produced, peasants are burying it. The paste is made by the barefoot stomping of coca leaves in kerosene and acid to leach the leaf's active ingredient.

For now, it appears that Bolivian President Victor Paz Estenssoro has gained an edge over cocaine traffickers in his daring decision to attack them and attempt to alter the economics of coca production here. But the triumph is only a first and tentative blow in what has become a two-front war for him.

One battleground is the pervasive cocaine trade, whose practitioners are amassing enormous economic influence in this undeveloped country -- the poorest in South America -- and whose drug is poisoning Bolivia's youth, many of whom smoke pitillos, cigarettes laced with coca paste.

The other is the legitimate economy, which shows no sign of growth. But Paz Estenssoro has cured it of what was the world's highest inflation rate.

As the president nears the August anniversary of his first year in office, some Bolivians worry that the veteran politician -- at 78, he is South America's oldest president -- has taken on too much by seeking to shrink the lucrative cocaine business without a concurrent expansion of legitimate economic sectors.

In fact, Paz Estenssoro's decision to go after the drug smugglers went against the advice of at least one close aide. "Running the economic side," recalled Planning Minister Gonzalo Sanchez de Losada in an interview, "I said to Dr. Paz, when we're fighting bare-handed with a tiger, we don't take on an alligator."

The white-haired, pipe-smoking Paz Estenssoro seems to have been emboldened to confront the drug barons by his success at flattening inflation, which has fallen from an annual rate of 23,000 percent to near zero.

This seemingly miraculous drop was achieved by the strict application of orthodox economic remedies, including a freeze on wages in the public sector and an increase in public-sector prices, such as for gasoline, to correct a large and chronic budget deficit. In addition, the peso, devalued 95 percent against the U.S. dollar within days of Paz Estenssoro's inauguration, was allowed to float freely on foreign exchange markets.

More recently, the Bolivian leader pushed through Congress legislation to tax houses, cars and other personal property as a further means of raising state income. Bolivia has had the lowest per-capita tax rate of any country in the world, according to a World Bank study.

The problem now for Paz Estenssoro is how to revive the legal sectors of the economy. His impressive restoration of monetary stability has been rewarded by a new $50 million standby credit from the International Monetary Fund and a 10-year agreement with major creditors rescheduling arrears on the $3.4 billion foreign public debt. (Bolivia owes another $600 million to foreign private banks, which have not received any payments of principal or interest since 1984.)

But possible engines for economic growth are few. The mining industry, Bolivia's traditional economic mainstay, has been hard hit by a collapse of world tin prices and faces the probable layoff of half or more of its 30,000 workers.

The president is counting on several projects to spur Bolivia forward, including the planned development of lithium and potassium reserves, anticipated increases in meat sales to Peru and Chile, the possible expansion of soy bean cultivation and the hoped-for construction, currently under negotiation, of a pipeline from Santa Cruz, Bolivia, to Sao Paulo, Brazil, to supply Brazil with natural gas.

"It's very dangerous to make economic or political forecasts in Bolivia," said Paz Estenssoro in an interview last week. "But with a large margin for error, Bolivia in one year will begin to feel the effects of the measures we're taking."