More than 2,200 federal, state and local law enforcement agents began a nationwide series of raids on marijuana fields yesterday in the largest crackdown on domestically grown marijuana.

Attorney General Edwin Meese III had planned to lead the raids by accompanying agents to a remote marijuana field in the Ozark National Forest in northern Arkansas. But after heavy rains threatened to cause flash flooding in the area, Meese viewed the operation by helicopter.

The raids, code named "Operation Delta-9," were planned for all 50 states in an effort to destroy up to 250,000 marijuana plants over a three-day period. Officials said that further raids will continue throughout the marijuana harvesting season, which extends through October.

In a news conference in an airplane hangar in Harrison, Ark., Meese said the program was aimed at "increasing the cost to drug traffickers and eradicating marijuana crops in the United States."

"We are sending a strong message, both to the domestic producers of marijuana and to the source countries outside our borders, that the U.S. government takes very seriously the need to attack the production of this drug," Meese said.

John C. Lawn, head of the federal Drug Enforcement Administration, who accompanied Meese on the trip, estimated that 12 percent of the marijuana consumed in the United States is domestically grown. He said drug dealers are turning to domestic crops because of the federal government's successful interdiction of shiploads of marijuana from South America and elsewhere.

Meese said that agents planned to raid hundreds of sites where marijuana has been sighted, including 22 in national forests. According to agency spokesmen yesterday, the raids were going as scheduled, with no violence or resistance from the growers.

Meese said he regards marijuana operations in national forests as particularly dangerous because of the possibility that innocent people might accidentally discover the drug traffickers. "The threat to public safety . . . is very serious. A family picnic or backpacking trip can become a horrible nightmare," he said.

Lawn said domestic growers, many using federal lands, have been known to place booby traps near the crops, such as eye-level fishhooks, to deter intruders.

Meese also said that "too many people regard marijuana lightly, wrongly believing it to be on a par with alcohol."

The current series of raids is being conducted using manual means -- including chopping down the plants or pulling them out of the ground. Lawn is scheduled to decide by the end of the month whether to resume the controversial practice of eradicating marijuana fields by spraying herbicides, including paraquat.

Lawn said the federal agency's marijuana eradication effort is not a new program, but this is the first time that raids are being conducted in all 50 states.

The agency's eradication effort last year destroyed 13 million marijuana plants and led to the arrests of 4,941 people