When Maj. Hal Sellers learned his infant son was living on borrowed time awaiting a heart transplant, the Marine and his wife had to choose between duty to family and to nation.

Sellers "did a lot of soul-searching" when the time came to decide, said his wife, Betsy Sellers. Unable to help the youngest of the couple's three sons, he chose to help his unit.

A little more than a week after his departure, baby Dillon has days to live unless he receives a new heart.

"I am doing what I have to do, and my husband is doing what he has to do," Betsy Sellers, 37, said Monday. "We're doing what we need to do for our family and, hopefully, for other families."

"It was a hard decision to make. He had to come to the hospital and say goodbye to Dillon, and not know what would happen."

Four-month-old Dillon was 10 days old when he was diagnosed on Oct. 31 with Hypoplastic Left Heart Syndrome, which occurs when a heart is unable to pump or circulate blood. Although the condition can sometimes be corrected with surgery, Dillon's heart is too damaged, doctors say.

Dillon, who is in critical condition, has been placed at the top of the heart transplant list at Loma Linda University Medical Center, which has a 25 percent mortality rate for those awaiting transplants.

"Every day could be an end-of-life issue for him," said the medical center's transplant coordinator, Armando Deamaya . "We're probably talking days rather than weeks."

His father was offered a desk job at the Marine Corps Air Ground Combat Center in Twentynine Palms, but the 13-year veteran opted to go with the 3rd Light Armored Reconnaissance Battalion to an undisclosed location in the Middle East.

Sellers, 37, second in command of the unit, had trained for months for the deployment and was concerned about bringing in a new member so late in the training, his wife said.

"I think this situation sheds light in a very tangible way on the sacrificial nature of service to country. While no one would want to be in the major's position, we understand the difficulties," said Capt. Rob Crum, a base spokesman.

The major's mother, Betty Sellers, said the family supported her son's decision.

"We didn't say, 'Hal, do this or do that.' We tried to convey the message that Dillon was getting the best possible care he could have, and maybe Hal had to do in life what he could do best," she said in a telephone interview from her home in Des Moines, Iowa.

Lying in a crib at the medical center, Dillon breathes with the help of a ventilator as tubes snake from his chest, arms and legs. A patch from Sellers' unit, known as the Wolf Pack, is among the pictures and stuffed animals decorating the boy's crib.

On Sunday, Sellers called home from an undisclosed location for an update on Dillon.

His wife delivered a message to their son: "Daddy loves you."