On 22 March, the US Supreme Court is scheduled to hear the case of a convicted killer from Texas who is mentally handicapped.
The court issued its order two hours before Antonio Richardson, 26, was due to be executed for his role in the 1991 rape and murder of two sisters.
The court order came just hours after Georgia's highest court issued a stay of execution in another case, while it considers whether the electric chair constitutes "cruel and unusual punishment", an action barred by the US Constitution.
Either execution would have been the 700th since the US reinstated the death penalty in 1976.
Grounds for clemency
Richardson's lawyers appealed for clemency on three grounds
The human-rights organisation Amnesty International, which campaigns against the death penalty, says international law prohibits the execution of people who were under the age of 18 at the time their crime was committed.
On 22 March, the US Supreme Court is scheduled to hear the case of a convicted killer from Texas who is mentally handicapped.
The court's decision could have implications for the Richardson case.
The age factor in the Richardson case could have ramifications in turn for the case against a 15-year-old boy who stands accused of carrying out a lethal shooting spree in California on Monday.
Rape and murder
Richardson is one of four people sentenced for the 1991 rapes and killings of Robin Kerry, 19, and her sister Julie, 20.
The women were pushed off an abandoned bridge to their deaths. Richardson was not accused of pushing them.
Two of his accomplices were also sentenced to death, while a third got 30 years in jail after agreeing to testify.
In Georgia, the state supreme court issued a stay of execution for Ronald Spivey, 61, by a vote of four to three.
Spivey was convicted of killing a policeman in 1976.
Georgia is one of four states that uses the electric chair. It has switched to lethal injection for crimes committed after 1 May 2000, but still electrocutes criminals convicted of crimes before that date.
Amnesty International has called on the US to ban the death penalty.
It describes execution as "a cruel, brutalising, unreliable, unnecessary and hugely expensive activity for no measurable gain".
But the Richardson and Spivey stays will almost certainly not prevent the US from executing its 700th person this week, probably as early as Wednesday.
On Wednesday, Texas is scheduled to execute Dennis Dowitt, 55, for the murder of a teenaged girl in 1990.
Three further executions are scheduled for later in the week, in Oklahoma, North Carolina and Delaware.