BRUSSELS — Belgian lawmakers clashed on Wednesday over whether to grant terminally ill children the right to ask to die, a legal option already possessed by the country’s adults.
The issue pits backers who see it as a question of mercy against opponents who say the measure is flawed and lacking medical rationale.
Despite spirited debate in the House of Representatives, the bill is widely expected to pass on Thursday.
‘‘Our responsibility is to allow everybody to live, but also to die, in dignity,’’ said Karine Lalieux, a Socialist member of the House who favors extending Belgium’s 2002 euthanasia law to minors under 18 — with the conditions that their parents approve and that they understand what the decision means.
Sonja Becq, a Christian Democratic colleague, denounced the potential change, saying science is capable of relieving pain in very sick children until their illnesses run their natural course.
‘‘We cannot accept that euthanasia be presented as a ‘happy ending,’ ” she said.
Belgium sets legal limits on who can legally acquire cigarettes and alcohol, she said — so why not for euthanasia?
The Senate adopted the legislation in December. If it passes in the House, all that would be needed for child euthanasia to become legal in Belgium is the signature of King Philippe, normally a formality.
The only other countries to have legalized euthanasia are the Netherlands and Luxembourg.
In the Netherlands, children 12 to 15 may be euthanized with parents’ permission; those who are 16 or 17 must notify their parents beforehand.
To guarantee that sick children understand what euthanasia signifies, Belgium’s bill would require them to demonstrate to a psychologist or psychiatrist that they possess the ‘‘capacity of discernment.’’
Parents would have to agree with the child’s choice.
As with adults who seek euthanasia, children would have to be in a state of unrelieved suffering, be afflicted with a terminal illness, and be near death.
Foes in the House said the proposal was full of holes.
‘‘Can you tell me what a ‘state of discernment’ means?’’ Becq asked.
Does near death mean ‘‘three days, three weeks, six months?’’ asked Steven Vanackere, a Christian Democrat.
Daniel Bacquelaine, of the centrist Reform Movement, tried to assuage the fears.
‘‘Where there is the smallest doubt about the discernment of the child, the question of euthanasia will not be posed,’’ he said.
The same goes when there is a glimmer of medical hope for the survival of the patient, he said.
Though one survey found 75 percent of Belgians favor extending the euthanasia law to children, there has been vocal opposition, with Andre Leonard, the Roman Catholic archbishop of Mechelen-Brussels, in the vanguard.
This week, an ‘‘open letter’’ carrying the names of 160 Belgian pediatricians was issued to argue against a new law, saying there is no urgent need for it.
Some doctors have come out in favor, and say that only a handful of children, all teenagers, would be entitled to seek application of the euthanasia law each year.
Dr. Marc Van Hoey, a general practitioner who is president of the Right to Die Association in the region of Flanders, is in favor of the legislation. Euthanasia, he said, sometimes becomes the kindest and most caring option.
‘‘I've seen quite a lot of persons dying in — how do you say in proper English — agony?’’ said Van Hoey. ‘‘If you see somebody who died in pain, you see his face completely with a kind of expression where you see the pain on the face.
‘‘I never saw that when I gave someone euthanasia he or she asked for,’’ the doctor said.