American agencies coordinating the emergency-relief operation for victims of the Mexican earthquake repeated their plea yesterday to private donors: Send money, not supplies.

The Agency for International Development (AID) and the American Red Cross said they are responding to specific requests for assistance from the Mexican government and warned against donations of food and clothing that could choke fragile supply lines.

First Lady Nancy Reagan, visiting quake survivors in Mexico City, delivered a $1 million check for relief efforts. The money, which came from AID funds, was described by her chief of staff, James Rosebush, as "just a down payment."

Relief agencies and governments around the world have given or pledged several million dollars in assistance to Mexico since Thursday's earthquake.

Among the biggest so far is a $2.5 million cash pledge by the Japanese government, while the League of Red Cross and Red Crescent Societies said it has sent cash donations from members totaling $1.43 million to the Mexican Red Cross.

Yesterday a Los Angeles City Council member, Art Snyder, just back from Mexico City, said that medical supplies and heavy construction equipment are badly needed.

In Geneva, the U.N. Disaster Relief Organization appealed for emergency medical supplies and additional equipment to clear the rubble in the quake-ravaged area, United Press International reported.

"We do not need any more volunteers, but more medical and rescue equipment as soon as possible," said the organization's director general Hans Einhaus.

The American Red Cross in Washington said that its 10-member team in the disaster area had reported via a portable satellite dish that local relief agencies were coping better than had been expected.

"There are a lot of well-meaning people in the United States offering food and blankets," said American Red Cross spokesman George Cleland, "but it is not needed."

Private agencies in the United States already have sent hundreds of thousands of dollars and tons of supplies, from syringes to canned food, to Mexico City.

The spontaneous American relief effort has ranged from ham operators on both sides of the border feeding scarce information on survivors, to radio, TV stations and churches throughout the country raising tens of thousands of dollars.

In New York, Cardinal John J. O'Connor said that each of the 411 parishes in his archdiocese would start a fund-raising effort and would pass the money to Cardinal Ernesto Corripio in Mexico City.

In New Jersey, the pharmaceutical giant, Johnson & Johnson, said that it has authorized its Mexico City plant, which was slightly damaged in the quake, to donate supplies as needed.

The official American response has been more cautious, waiting for each Mexican request as it comes in by the hour. On Sunday, Air Force planes delivered 100 five-gallon plastic water containers, 200 pairs of rubber gloves, 600 sleeping bags, 600 jackets and 300 cots, according to Betty Snead, a spokeswoman for AID.