"Mi casa es su casa," President Ronald Reagan said to Mexican President Jose Lopez Portillo over lunch at the White House yesterday. "My house is your house."

For yesterday's midday meal, it seemed that it was. The two presidents disagree on major foreign policy issues, but these were glossed over by the bright day and chilled wine. From Lopez Portillo:

"We have spoken about many things." he said in his toast to Reagan. "Fortunately, we have agreed on most of them. We have dissented on some. But with the greatest respect we have agreed to talk about the matters on which we dissent in order to fine appropriate solutions."

Lopez Portillo's toast, spoken through an interpreter, was a lot longer than Reagan's. At one point, he appeared to refer to the previous administration. "I had always spoken frankly," he said, "but I have always measured the weight of each of my words because the relationship for some reason or another had always been a tense one. A relationship between neighbors that are so different is always difficult . . . but I confess for the first time now, I have felt totally relaxed."

The lunch began at noon as a harpist played delicate tunes in the cool shadows of the White House diplomatic entrance, a circular room just off the South Lawn. One of the first people to arrive was a big, burly baseball player. Fernando Valenzuela rookie pitcher of the Los Angeles Dodgers.

"Of course I'm very proud," he said through his impromptu interpreter, John Gavin, the U.S ambassador to Mexico. Valenzuela is a big star in Mexico as well as in the United States, and was just about the biggest star at the White House yesterday.He signed three baseballs for Mexican journalist, cameras whirring.

At this point, Secretary of State Alexander Haig arrived. He stopped, posed for a few pictures with Valenzuela, then listened to the shouts from a pack of reporters behind ropes.

"Mr. Secretary, are you a baseball fan?"

"You betcha!"

"Did Israel violate restrictions on American arms?"

"Possibly."

"Might the U.S. cut off arms shipments to Israel?"

"I'm not going to get into that."

Haig was referring to Israel's weekend raid -- with American-supplied aircraft -- on an Iraqi nuclear plant, and what the U.S. response might be. "We have obligations to report possible violations," Hiag said as he headed up the marble stairs to the main floor of the White House, "and we're doing so."

Behind him came White House chief of staff James Baker and Attorney General William French Smith. Others on the guest list included golfer Lee Trevino, Joseph Allbritton of Allbritton Communications and columnist Clayton Fritchey, who's not a Republican.

"You're a Democrat!" somebody shouted at him.

"Shhhhhhh!" he replied.

Lunch, for 138 people, was king crab legs, veal, rice pilaf, spinach, raspberry mousse with fresh peaches, plus lots of wine. Everyone sat in the East Room at round tables with pink peonies and blue and white ribbons. Lopez Portillo's visit was a working visit and not a state visit, which is why he wasn't given a state dinner.

Still, strolling strings played during dessert, and when Lopez Portillo drove out the White House driveway in his limousine, guards held flags of the American states to mark the way. Just before Lopez Portillo's departure, Reagan stood on the steps of the North Portico, flags flapping, trees blowing in the warm wind, and announced results of his meetings with the Mexican leader.

"The talks that we've had were frank, they were valuable and they lead to a closer relationship between our two countries," he said.

In his toast to Lopez Portillo, Reagan told the story of a California mud slide and a Mexican man whose home was destroyed. "We were both knee-deep in mud," Reagan said. "It must have been heart-breaking for him because his home had obviously been newly furnished. Now it was a scene of ruin.

"With quiet dignity and the utmost serenity, he said, 'Governor Reagan, mi casa es su casa. My house is your house.'"

Guests tittered at this, the image being one of the White House in a mud slide. But Lopez Portillo saw it differently.

"For the first time, a president of the United States has used with me that very generous formula of 'My home is your home,'" he said. "For we who understand the greatness and dignity that there is behind that expression, what I have heard from the president today has deeply moved me -- as I can understand very well that he felt deeply moved also when he heard that old man who had no roof over his head, and who was offering him his home."

Guests at the White House luncheon for Jose Lopez Portillo, President of Mexico: Jorge Castaneda de la Rosa, secretary of foreign relations of Mexico. David Ibarra Munoz, secretary, for finance and public credit Jose Andres de Oteyza, secretary of patrimony and industrial development Jorge de la Vega Dominguez, secretary of commerce Pedro Ojeda Paullada, secretary of labor and social welfare Miguel de la Madrid Hurfado, secretary of programming and budget Rosa Luz Alegria Escamilla, secretary of tourism Fernando Rafful Miguel, chief, Department of Fisheries Oscar Flores Sanchez, attorney general The Ambassador of Mexico & Mrs. Margain Jose Ramon Lopez Portillo Romano, under secretary of evaluation of the secretary of programming and budget Roberto Casillas Hernandez, private secretary to the president Gen. Miguel Angel Godinez, chief of staff of the Presidential General Staff Rafael Lzquierdo, adviser to the president Luis Javier Solana Morales, coordinator of social communication, office of the president Jose Antonio Ugarte Romano, adviser to the president Alfonso de Rosenzqeig-Diaz, under secretary for foreign relations Jorge Equardo Navarrete, under secretray for economic affairs, Office of Foreign Affairs Carlos Gonzalez-parrodi, chief of protocol Miguel Marin, private secretary to the foreign minister Andres Rozental, director general for North American affairs, Office of Foreign Affairs Miguel Lopez-Azuara, director general for information George Abbott and Mrs. Abbott, New York, N.Y. Dr. Hector R. Acuna, director, Pan American Health Organization, & Mrs. Acuna Joe L. Allbritton, chairman, Allbritton Communications Co., Washington, D.C., & Mrs. Allbritton Richard V. Allen, assistant to the president for national security affairs, & Mrs. Allen Mrs. Joseph Alsop, Washington, D.C. Everett Alvarez Jr., deputy director-designate, Peace Corps, & Mrs. Alvarez Martin Anderson, assistant to the president for policy development Leonore Annenberg, chief of protocol James A. Baker III, chief of staff and assistant to the president, & Mrs. Baker Secretary of Commerce Malcolm Baldrige & Mrs. Baldrige Hector Barreto, president, United States Hispanic Chamber of Commerce, & Mrs. Barreto Secretary of Algriculture John R. Block & Mrs. Block William E. Brock III, United States trade representative Rep. Clair Burgener & Mrs. Burgener Vice President & Mrs. Bush John Ellis Bush & Mrs. Bush, Miami, Fla. Jose R. Cano, national chairman, American G.I. Forum of the United States Joseph W. Canzeri, duputy assistant to the president and assistant to the deputy chief of staff Michael Cardenas, administrator, Small Business Administration Eugene Carusi & Mrs. Carusi, Washington, D.C. William P. Clark, deputy secretary of state, & Mrs. Clark Gov. William Clements of Texas & Mrs. Clements Helen Copley, chairman, The Copley Press Inc., La Jolla, Calif. Richard G. Darman, deputy assistant to the president and deputy to the chief of staff Michael K. Deaver, deputy chief of staff and assistant to the president, & Mrs. Deaver. Rafael de la Colina, permanent representative of Mexico to the OAS, & Mrs. de la Colina Rep. Eligio de La Garza & Mrs. de La Garza Tirso del Junco, chairman, California Republican Party, & Mrs. del Junco, Los Angeles, Calif. Antonio DeMarco, Los Angeles, Calif. Sen. Peter V. Domenici & Mrs. Domenici Glenn S. Dumke, chancellor, California State University & Colleges, & Mrs. Dumke Secretary of Energy James B. Edwards C. Allen Ellis & Mrs. Ellis, New York, NY. Thomas O. Enders, assistant secretary of state-designate for inter-American affairs, & Mrs. Enders Clayton Fritchey & Mrs. Fritchey, Washington, D.C. Craig L. Fuller, deputy assistant to the president and director of the office of Cabinet administration John A. Gavin, American ambassador to Mexico Secretary of State Alexander M. Haig and Mrs. Haig Sen. S.I. Hayakawa Joseph J. Jova, president, Meridian House International, & Mrs. Jova Michael J. Kelly, chairman, Kelco Industries, & Mrs. Kelly Secretary of Transportation Andrew L. Lewis Jr. Rep. Tom Loeffler & Mrs. Loeffler Bernard Blas Lopez, executive director, New Mexico Arts Division, State Arts Council, Santa Fe, & Mrs. Lopez Gorgon C. Luce & Mrs. Luce, San Diego, Calif. Rep. Manuel Luian Jr. Sarah McClendon, McClendon News Service, Washington, D.C. Edwin Meese III, counselor to the president, & Mrs. Meese J. William Middendorf II, permanent representative of the USA to the OAS-designate, and Mrs. Middendorf Lauro J. Neri & Mrs. Neri, Covina, Calif. Jeremiah O'Leary & Mrs. O'Leary, The Washington Star Lionel Olmer, under secretary of commerce of international trade Antonio Ortiz Mena, president, Inter-American Development Bank, & Mrs. Mena Myer Rashish, under secretary of state for economic affairs Secretary of the Treasury Donald T. Regan & Mrs. Regan Pedro San Juan, assistant secretary for the interior-designate for territorial and international affairs & Mrs. San Juan Sen. Harrison Schmitt Attorney General William French Smith Larry Speakes, deputy press secretary to the president George Strake, secretary of state, Texas, & Mrs. Strake Henryk Szervng, violinist; Mexican delegate to UNESCO Louis Terrasas, president, Gold Mine Manufacturing Co., San Antonio Col. C. J. Tippett & Mrs. Tippett, Upperville Nicholas Thimmesch, Los Angeles Times Syndicate Sen John Tower & Mrs. Tower Lee Trevino, professional golfer, & Mrs. Trevino, Dallas, Tex. Charles P. Tyson, deputy assistant to the president for national security affairs Luis Valdez & Mrs. Valdez, University City, Calif. Fernando Valenzuela, pitcher, Los Angeles Dodgers Mrs. Jacobo Zabludowsky, Televisa-Mexican television network