President Bush pauses during remarks on his freedom agenda at the Ronald Reagan Building in Washington July 24, 2008. REUTERS/Jason Reed

WASHINGTON (Reuters) - President George W. Bush on Monday approved the death sentence of an Army private convicted of murder and rape in 1988, becoming the first U.S. president to approve a military execution in 51 years.

Bush signed a request by the military that Ronald Gray be put to death following his court-martial conviction 20 years ago on multiple charges of murder and rape.

“While approving a sentence of death for a member of our armed services is a serious and difficult decision for a commander in chief, the president believes the facts of this case leave no doubt that the sentence is just and warranted,” White House spokeswoman Dana Perino said a statement.

Unlike the civilian court system, the U.S. military justice system dictates that a member of the armed forces cannot be executed until the president approves the death sentence.

Citing expected legal challenges, Perino declined further comment on what would be the first U.S. military execution since 1961, when a convicted child rapist was hanged after his sentence was approved by President Dwight Eisenhower in 1957.

The last president to act on a military death sentence was John F. Kennedy, who commuted a death sentence to life in prison in 1962, according to White House records.

Gray was convicted by a court-martial at Fort Bragg, North Carolina of two murders, an attempted murder, and three rapes committed during a spree in 1986 and 1987.

He received multiple life sentences from the North Carolina state court and has been held on death row in a military prison in Kansas since April 1988.