U.S. Customs Commissioner William von Raab yesterday charged that "corruption and ineptitude" by Mexican law enforcement officials have allowed drug trafficking along the border to increase so much that it poses a "serious national security concern."

Von Raab, testifying before the House Select Committee on Narcotics Abuse and Control, said Colombian dealers are creating the kind of drug-trading zone that existed in southern Florida six years ago, when so-called cocaine cowboys engaged in daytime machine-gun shootouts in shopping centers.

"It is a modern-day horror story," von Raab said. "Smugglers have been building new landing strips in Mexico less than 100 miles south of our border. They are building warehouses to store vast amounts of drugs." The smugglers use small planes to fly to and from the United States, he said.

Leonardo French, a spokesman for the Mexican Embassy, said yesterday that "Mexico has done its best for many years and is firmly determined to continue to do so in the war against drug trafficking, but . . . it is indispensable to attack simultaneously all the links in the chain of this criminal activity, such as production, distribution, transportation, planning, financing . . . as well as to discourage demand and consumption. Most of these links do not have their bases in Mexico."

Yesterday's hearing was not the first time U.S. officials have complained about corruption among Mexican law enforcement officials. John C. Lawn, who heads the Drug Enforcement Administration, has been particularly critical of Mexico's investigation of last year's abduction, torture and murder of DEA agent Enrique Camarena Salazar, who was seized by drug traffickers on a busy Guadalajara street just outside the U.S. consulate.

Von Raab told the panel that Colombian traffickers buy the services of Mexicans to carry the drugs into the United States and to provide protection. "The Mexicans are, in effect, the freight forwarders and security services for Colombian drug-smuggling groups.

"If law enforcement can be so easily bought by drug smugglers, it can just as easily be bought by terrorists," von Raab said.

"This is a terrorist threat by every definition, and if we ever hope to combat this threat to our nation, there must be a significant change in attitude from our southern neighbors," he said.

When committee Chairman Charles B. Rangel (D-N.Y.) said he had assurances from the State Department that "we're receiving top cooperation" from Mexico, von Raab replied, "The Customs Service is not receiving cooperation from Mexico."