In a motion filed Wednesday, lawyers for James Holmes said Holmes offered to plead guilty if he could avoid a death penalty and serve a sentence of life in prison without parole, The Denver Post reported.
The same offer was made before an arraignment hearing earlier this month, the motion said.
"Mr. Holmes is currently willing to resolve the case to bring the proceedings to a speedy and definite conclusion for all involved," the motion said.
The prosecution said it would announce during a court hearing Monday whether it would seek the death penalty. Prosecutors said they wanted to consult with survivors and victims' families.
Holmes is accused of killing 12 people and wounding 58 others when he opened fire in the movie theater July 20. He has been charged 166 counts of murder, attempted murder and other offenses.
In the motion, Holmes' attorneys said prosecutors haven't accepted the offer, the Post reported.
His attorneys say in the document they thought the case could be closed Monday.
"It appears the only impediment to a resolution of this case would be if the prosecution chooses to seek the death penalty," the lawyers wrote.
If prosecutors reject the offer, Holmes' lawyers said they may launch a mental health defense and would defend Holmes "vigorously."
A representative from the prosecutor's office said he couldn't comment on the motion because of a gag order.
A judge earlier this month entered a plea of not guilty to the charges on Holmes' behalf after his attorneys refused to enter a plea.
Holmes' trial is scheduled for Aug. 5 and is expected to last about a month.