Last month, nearly 30 years after her grandfather Ike retired from the White House, Susan Eisenhower and her new fiancé were invited to dinner by George and Barbara Bush. Though it was just a small gathering in the President's private quarters, the evening was not without global significance. "If you told me two years ago I would be walking through the White House with Eisenhower's granddaughter, I would have told you that you were crazy!" says the groom-to-be. Indeed, in a world before glasnost, Eisenhower's engagement would have been inconceivable; her intended is one of the Soviet Union's top space scientists, 57-year-old physicist Roald Z. Sagdeyev.

Now, with the Cold War on thaw, perestroika's happy pair are the toast of the superpowers. And plans for their Feb. 9 nuptials in Moscow have taken on summit dimensions, with a religious service and a reception planned at the U.S. Embassy after the couple tie the knot in a Soviet civil ceremony.

Eisenhower, 38, who runs her own consulting firm, advising companies on joint U.S.-Soviet ventures, met Sagdeyev in 1987 at a New York reception. He asked her to dance and got right down to business. "Do you think your grandfather was serious when he made that speech warning about the military-industrial complex?" he asked. Smoothly, Eisenhower replied that "the Soviets have their own military-industrial complex," she recalls. "I told him that profit isn't the only thing that drives vested interests."

Relations could only get warmer, and they did. The pair passed a pleasant evening, but Eisenhower was resistant when Sagdeyev invited her to Moscow for the 30th anniversary of the Sputnik launch. Then he told her, "You know, my country is like your country. We have good guys and bad guys. I'm one of the good guys. And you have to come help the good guys." Says Eisenhower: "He asked me to trust him, and I did."

Over the next year, the two met at a number of U.S.-Soviet conferences. Passing notes back and forth during these confabs, they discovered they often shared the same views. "I think we agreed more often than he agreed with his countrymen or I agreed with mine," Eisenhower says. Yet lingering taboos on superpower fraternization kept their romance from blossoming until last summer, after Eisenhower agreed to help Sagdeyev write his memoirs for Bantam. Shuttling between Moscow and Washington, they fell in love over the tape recorder.

"He would be back in the Soviet Union and I would be listening to his voice on the tapes," says Eisenhower. "The more I listened, the more I realized not only how exceptional he is in his own country but by any standard." Meanwhile, their phone bills were growing faster than the defense budget—hers topping $600 one month. "Over the course of time," says Eisenhower, "we realized how much we missed each other and how much better we are together."

Sagdeyev graduated from Moscow University with a degree in theoretical physics in 1956, the year Eisenhower's grandfather was elected to a second term. After working at the Soviet Institute of Atomic Energy, he moved to Siberia, where he founded a think tank far from the stifling party politics of the Soviet capital. By 1973 he was being called back to Moscow to rescue the struggling Soviet space program, which he rebuilt over the next 15 years. Married for 30 years, he has a son and a daughter, both computer scientists. He was divorced in 1989 but feared that the Politburo might disapprove of his romance with Eisenhower. Together, on one of her Moscow visits, they tested the waters by telling an old friend, a high-ranking party official. "He was absolutely silent for a while," says Sagdeyev. "It was kind of like an earthquake. Then he said, 'I'm going to have to think about this.' " Two months later, Sagdeyev got the party's blessing.

Eisenhower has been married twice before and has three daughters, ages 8 to 17. Her two oldest children were born during her seven-year marriage to Alexander Bradshaw, the son of a British consul in Belgium, who later became a Catholic priest; that marriage ended in 1977. She then married lawyer John Mahon, whom she divorced seven years ago. Since then Eisenhower has been raising her daughters with the help of housekeeper-nanny Delores Moaney, 72, who has been with the Eisenhower family 43 years. Eisenhower and Sagdeyev will divide their time between Moscow and Bethesda, Md., where the girls are in school. Her daughters, says Eisenhower, "know Roald and enjoy him immensely."

In retrospect, the happy couple are a bit embarrassed by how much time they spent worrying about the political implications of their union. "It is unbelievable how quickly people accepted this," says Sagdeyev. "We are just two people, after all, so why were we taking into consideration all these other issues, like nuclear deterrence?" Love is a simpler calculus, as Eisenhower's grandfather observed long ago. "People want peace so badly," Ike once said, "that someday governments are going to have to get out of the way and let them have it."

—Montgomery Brower, Jane Sims Podesta in Washington, D.C.