The US Supreme Court has cleared the way for Tennessee inmate Christa Pike to be executed, overturning a last-minute reprieve.

The killing by lethal injection was scheduled for Wednesday morning before judges from the Sixth Circuit Appeals court halted the execution. Tennessee's attorney general then immediately requested the Supreme Court to overrule the lower court's stay.

Pike, 50, has been awaiting execution since she was convicted and sentenced to death in 1996 for the murder of Colleen Slemmer.

If the execution proceeds, Christa Pike will be the first woman to be executed in Tennessee in more than 200 years. It was not immediately clear when the execution would take place.

Supreme Court Justice Brett Kavanaugh granted the application to vacate the stay of the execution. No explanation for lifting the stay was provided in the order.

The top court's three liberal justices - Justices Sonia Sotomayor, Elena Kagan and Ketanji Brown Jackson - dissented in Wednesday evening's order.

Sotomayor wrote that she dissents because the decision cleared the way for Tennessee to execute Pike before her pending legal challenges to her conviction "can be properly considered".

"Tennessee's desire to expedite Pike's execution by a few days or even weeks cannot outweigh her 'fundamental interest in [her] own life," she said.

The latest ruling from the Supreme Court came just before 18:00 local time, hours before the state's execution order is set to expire at midnight. If time runs out the Tennessee Supreme Court will need to set a new execution date, the Associated Press reports.

In a ruling earlier on Wednesday, judges from the Sixth Circuit Appeals court paused the execution saying they needed more time to consider the arguments in Pike's case.

Pike's lawyers said that for years, the state of Tennessee argued in court that she had lied about being sexually abused as a child.

But at a recent hearing about her execution method, the state said it did not dispute she suffered sexual abuse and rape.

Pike's legal team asked the appeals court to send her motion back to the district court, arguing that if the federal courts based their ruling on the state's earlier claim that she was lying, then the federal review was affected.

Earlier this week, the Supreme Court refused to hear a different appeal from Pike.

Tennessee governor also denied a clemency request this week from the death row inmate.

Pike was 18 when she and her then-boyfriend, Tadaryl Shipp, beat, tortured and murdered Colleen Slemmer, a 19-year-old they met at a job training camp for troubled teens.