Cardinal Norberto Rivera Carrera confirmed the Church's opposition to euthanasia in his homily on Sunday.
"Euthanasia is one thing," the cardinal said, "dying well is another."
The bill, introduced by the Democratic Revolution Party, would permit terminally ill patients to renounce every form of medical care to prolong life. If the patient is unable to make the choice, an immediate member of the family could decide on his behalf.
The legislation stipulates that there will be juridical protection for doctors willing to permit death to occur by withholding basic necessities, such as food and water.
The bill will be forwarded Wednesday to the legislature, where the Democratic Revolution Party holds a majority.