LIMA, PERU, NOV. 3 -- U.S. hopes to eradicate Peru's coca fields soon have faded with a decision by Peruvian officials that the best solution is a long-haul program to convince peasants not to grow coca.

A new anti-drug policy announced last week by President Alberto Fujimori states that growers of coca, from which cocaine is made, must be led to switch crops voluntarily and that any programs to wipe out the coca fields "that leave the peasants without alternatives could easily unleash a civil war of unforseeable proportions."

Fujimori proposes an extensive development effort and new talks about aid with U.S. officials. U.S. Assistant Secretary of State Melvin Levitsky, the State Department's chief official for anti-drug policy, met with Fujimori here this week and agreed to set up new bilateral "working groups" to shape future aid programs.

Sources said that Levitsky warned, however, that the United States expects tangible progress if U.S. aid is to continue.

Fujimori's new policy confirms what U.S. officials have gradually come to accept -- that the prospect of wiping out the coca fields, preferably by spraying them with herbicide, is unrealistic, given Peru's precarious political and economic circumstances.

Peru produces 60 percent of the world's coca, most of it in the remote Upper Huallaga Valley on the eastern slopes of the Andes, a stronghold of the Maoist Shining Path guerrillas. The government is concerned that cracking down on the estimated 200,000 families that depend on coca for their livelihood will create more recruits for the insurgency.

The new drug policy is Fujimori's first major statement on drugs since he took office last July. It comes in the wake of his decision to reject nearly $36 million in U.S. military aid for the anti-drug fight because he believed the package did not include enough funds for development.

Efforts by U.S. Drug Enforcement Administration agents to help the Peruvian police disrupt trafficking networks will continue. But neither U.S. nor Peruvian officials believe that in the long run these efforts will significantly decrease the coca supply, which in recent years has been expanding.

Fujimori's new plan states that there is currently no effective way of convincing coca growers to switch crops and that significant improvements in infrastructure and bureaucratic reforms will be needed before progress is made.

The plan, which is consistent with Fujimori's previous statements on the drug issue, looks at the coca growers as part of the "informal" economy of street vendors and bootstrap entrepreneurs. It states that one major obstacle to convincing the peasants to switch crops is the fact that most have no legal title to their land. Another is that "while coca is bought and sold in a free market, substitute products must pass through markets that are overregulated and captive."

Fujimori proposes to give the peasants legal ownership of their land, deregulate markets and eliminate layers of corrupt bureaucracy that thwart attempts to grow legitimate crops.

In addition, Fujimori says that new roads and other transportation facilities are needed if the growers of the Upper Huallaga Valley are to have any way of bringing substitute crops to market. Coca is taken out of the valley by traffickers who use small planes and clandestine airstrips, an alternative that would not be available for marketing other crops such as fruit or palm oil.

Coca also provides the Peruvian economy with at least $1 billion a year, and losing that income would have a serious impact on the nation's trade balance. Fujimori suggests looking at the drug trade within the context of the Bush administration's initiatives on Latin American trade and Third World debt relief. The United States had planned to offer Peru $39 million in military aid for the 1991 fiscal year, but in the wake of Fujimori's rejection of the 1990 military aid it is unclear just what will happen to those funds.