U.S. and Mexican officials yesterday urged a halt to gifts of food and clothing for earthquake-rocked Mexico City in favor of cash gifts to relief agencies, and said their top priority was saving those buried alive in the rubble.

Mexico's minister of tourism, Antonio Enriquez Savignac, who flew to Houston yesterday to get around communications problems in his capital, said the government needs "heavy-duty cranes, hydraulic jacks and any type of equipment that can be used to lift heavy rubble" because the immediate problem is to rescue those still trapped in collapsed buildings and then to demolish the structures.

State Department officials, echoing his message at a briefing here, said they had already sent a team of search-and-rescue and demolition experts and other emergency aid requested Friday evening by the Mexican government. Israel also sent an army team with sensor devices to locate survivors.

President Reagan announced that his wife Nancy would fly to Mexico Monday to "express the support of the American people."

"The desire to be a good neighbor is basic to the American character and to our foreign policy," Reagan said in making the announcement during his weekly radio address.

Savignac said the Mexican government has set up a reconstruction trust fund through which all financial contributions should be channeled. Officials here, meanwhile, urged that gifts be limited to money contributions to private agencies. They cautioned against free-lance efforts to ship food or clothing into Mexico and advised against unannounced good-will expeditions as well.

"The airports in Mexico City are open and functioning, but it is not helpful for people simply to arrive in Mexico without coordinating" their plans with Mexican officials, Assistant Secretary of State for Inter-American Affairs Elliott Abrams said at a midafternoon press briefing. "We need to look to them for requests."

M. Peter McPherson, head of the Agency for International Development, which is coordinating official U.S. assistance, said 40 disaster specialists were on their way to Mexico this weekend in response to the initial Mexican request. These included three U.S. Forest Service fire-fighting spray helicopters from California, teams from two heavy-duty demolition companies, a five-member search-and-rescue group from the Bureau of Mines and the Westinghouse Co., along with four dogs and their handlers to search for the missing.

Another Mexican government request received here late yesterday added a long list of items, from a military field hospital and two field kitchens to tool kits, cable cutters and heavy duty picks. McPherson said he would be "very unhappy" if all these were not on their way within 24 hours.

A 60-member State Department task force, meanwhile, has been receiving about 20,000 calls a day inquiring about relatives and friends in Mexico on a special number, 202-653-7959. Abrams said they could handle calls only about American citizens, about 2,000 of whom have already called the U.S. Embassy in Mexico City to say they are all right. Five Americans were reported to have died as of last night. Three were identified as Mary Elizabeth Vallejo, 34; her daughter, Ilse Anne, 8, and son Alonso, 5. The identities of the other two were not immediately available.

Savignac said those seeking information about Mexican friends or relatives should contact the nearest Mexican consulate so inquiries could be flown in by diplomatic pouch.

Officials of the American Red Cross, CARE and Catholic Relief Services said they have committed a total of $400,000 so far and all three organizations have sent teams to Mexico to assess further needs. Roman Catholic Archbishop Roger Mahony of Los Angeles sent $100,000 to church officials in Mexico City. In El Paso, Tex., Roman Catholic bishop Raymundo Peno called for a special collection.

Ford Motor Co. said it sent two planeloads of medical supplies to Mexico, and General Motors Corp. contributed $100,000 to the American Red Cross relief fund. Both companies have operations in Mexico.