Jean Nguyen and Clara Hale, born more than a half-century and a hemisphere apart, were each cited as "an American hero" by President Reagan last night.

The president's introductions of Nguyen, a Vietnamese refugee who is to graduate from West Point in May, and Hale, who founded a home in New York City for the children of drug addicts, came at the conclusion of his State of the Union address. The two women were seated in the House gallery between Maureen and Nancy Reagan.

"Jean, Mother Hale, your lives tell us that the oldest American saying is new again -- anything is possible in America if we have faith, the will and the heart," Reagan said in introducing the women.

"I don't know how a hero feels," Hale said later. "I know I'm just excited."

She said she did not know why Reagan chose her for the honor. "So many black people have done so many good things," she said, "I couldn't understand why he invited me."

But, she added, "He's the president and everybody looks up to him, so it's kind of nice that he picked me."

In a telephone interview last night, Nguyen, 21, said "it was my honor to be there" in the House chamber, but added that it was her father's decision to leave Vietnam that made it possible.

She said her father, Van Minh Nguyen, a former colonel in the South Vietnamese army, "didn't want to leave Vietnam , but he looked at the children and he wanted his children to have a future."

Hale and Nguyen said they were contacted by the White House on Friday.

But they were told that their visit to Washington was to be kept confidential.

Nguyen informed her family on Sunday, but told them to keep it secret, her father said last night in a telephone interview from Milton, Pa.

"I am so proud, not only for my family, but for the Vietnamese people," the elder Nguyen said.

Minh Nguyen graduated from the Vietnamese military academy, an example his daughter said led her to seek an appointment to West Point.

She was to return there early today to take examinations.

Hale and her daughter, Lorraine, are to meet with the president and Mrs. Reagan at the White House, however.

Hale, 79, who said she almost missed coming here because of her high blood pressure, said she probably will be too nervous to talk with Reagan.

"I'll let my daughter do all the talking," she said. "I take care of the babies and just enjoy myself. All I know is baby talk."

Despite her protestations, Hale seemed to have no trouble conversing with Nancy Reagan last night. Hale described the first lady as "nice and very sincere," and said they talked extensively about the possibility of Mrs. Reagan visiting Hale House soon.

"She said she wanted to come see me," Hale said. "I want her to see the house and the children."

In introducing the women last night, Reagan described the circumstances that brought Nguyen and her family to the United States.

"Ten years ago, a young girl left Vietnam . . . part of the exodus that followed the fall of Saigon," he said.

Nguyen, then 12, fled with her father, a former South Vietnamese army colonel, her mother, two brothers and three sisters.

Her father had threatened to kill the family with a mine rather than allow them to be captured by the communists.

They left their home in the Mekong Delta on a helicopter that island-hopped in the South China Sea for two days before they finally found a boat they could board.

After a week on the ship, the family reached the Philippines; two weeks later, they and 4,500 other "boat people" were moved to Guam.

The family next had a short stay at Fort Chaffee, Ark., before being sponsored by a Lutheran church in Milton, Pa.

One of Nguyen's brothers and two of her sisters have completed college. Her other brother is at Susquehanna University in Selinsgrove, Pa., and one sister remains at home.

"Just 10 years from the time she left Vietnam she will graduate from the United States Military Academy at West Point. I thought you might like to meet an American hero named Jean Nguyen," Reagan said, to a roar of applause.

Hale wiped away a tear as Reagan introduced her.

"She lives in the inner city, where she cares for infants born of mothers who are heroin addicts," Reagan said of the woman more than 500 foster children have known as "Mother Hale."

Many of the children were born addicted to drugs.

After caring for foster children to earn money to raise her own three children, Hale began her work with the children of women addicts in 1969, when one of her daughters sent a young addict and her child to Hale.

She took the child in, and within weeks had requests to care for more.

About 15 children are usually in residence at the Hale House, where they are cared for by a staff of 15. Most of the children stay about 18 months, and almost all of them are returned to their mothers.

Statistics compiled in 1984 showed that of 497 children who had lived at the home, only 11 were placed in adoptive homes.

Lorraine Hale, who has a doctorate in child development from New York University, coordinates the program, which is financed by a grant from the City Human Resources Administration and private gifts.

"Go to her house some night," Reagan said, "and maybe you'll see her silhouette against the window as she walks the floor, talking softly, soothing a child in her arms."

Reagan has made similar introductions in previous State of the Union addresses, and reporters were forewarned that more "heroes" might surface last night.

In February 1982, Lenny Skutnik, who a month earlier dived into the frozen Potomac to rescue a passenger from the Air Florida plane crash, and Sen. Jeremiah Denton (R-Ala.), a prisoner of war in South Vietnam for 7 1/2 years, became the first "heroes" to be honored by Reagan.

Last year, the president recognized Sgt. Stephen Trujillo, an Army medic who took part in the invasion of Grenada; Rev. Bruce Ritter, who works with abused children, and Dr. Charles Carson, who is studying computer-controlled walking for paralyzed persons.