Lawyers for Lisa Montgomery, slated to be the first woman executed by the US federal government in decades, sought clemency from President Donald Trump Tuesday claiming she was profoundly mentally ill when she committed murder in 2004.

In a last-ditch effort to prevent her execution going ahead on January 12, they told Trump in a letter that Montgomery was born brain-damaged and endured a life of extreme abuse before committing her crime.

"Broken before she was born, Lisa Montgomery's life was filled with torture, terror, failure, and betrayal," they wrote.

"You alone have the power to temper Justice with Mercy," they wrote Trump.

"You alone have the power to send a message to the thousands of women who have been the victim of childhood rape and trafficking that their pain matters -- that they matter -- that their lives have value."

They requested Trump commute her death sentence to life in prison without parole.

Montgomery, 52, was sentenced to death for the murder of a pregnant, 23-year-old Missouri dog breeder, Bobbie Jo Stinnett.

The crime was particularly gruesome and pre-meditated.

Under the guise of buying a puppy, Montgomery went to Stinnett's home, where she strangled her to death, and cut the baby from her body.

She then travelled back to her home in Kansas and told her unsuspecting husband that the baby was hers.

Montgomery's lawyers do not contest the facts, but say her defense was mishandled and the court ignored her history of mental illness.

Two prosecutors who have dealt with similar cases supported the clemency request.

"We know from first-hand experience that these crimes are inevitably the product of serious mental illness. Women who commit such crimes also are likely to have been victimized themselves," they wrote.

"These are important factors that make death sentences inappropriate."

The last woman to be executed by the US federal government was convicted murderer Bonnie Heady in 1953, according to the Death Penalty Information Center.

Montgomery is one of 13 federal death-row inmates whose executions the Trump Justice Department decided last year to go through with after a 17-year halt to carrying out death sentences.

The hiatus was prompted by questions about execution methods and broader opposition to the practice.

Ten have been executed since July and three more, including Montgomery, are scheduled before Trump's presidency ends on January 20.

A supporter of the death penalty, Trump has not intervened in any capital case.

Joe Biden, who will replace Trump as president in 15 days, opposes the death penalty and has criticized the Trump administration's resumption of executions.

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