Ms Englaro is said to have opposed being kept alive artificially
Italy's government has issued an emergency decree to prevent a woman who has been in a coma for 17 years from having her feeding tubes disconnected.
Last year the father of Eluana Englaro won a court battle allowing the hospital to let her die. The centre-right government opposed the move.
The new decree says food and water cannot be denied to a patient.
It was approved despite objections from Italy's president. The case has provoked fierce debate in the country.
Ms Englaro, 38, has been in a persistent vegetative state since a car crash in 1992.
Her father has been battling with the courts in Italy to let her die since 1999, insisting it was her wish.
In November, Italy's highest court ruled that she had expressed a preference for dying over being kept alive artificially, and that doctors could stop feeding her.
On Tuesday she was transferred to a private geriatric clinic in the northern city of Udine, where doctors had agreed to disconnect her feeding tubes.
But Friday's decree states that feeding "can in no circumstances be refused".
Prime Minister Silvio Berlusconi said: "Urgent government intervention is needed because this morning they began the non-provision of food and water to the person."
The BBC's Duncan Kennedy in Rome says the case puts Mr Berlusconi in direct conflict with the courts and President Giorgio Napolitano.
The prime minister said if the president persisted in refusing to sign the decree, an emergency session of parliament would enact a new law.
Although opinion polls in Italy show the public is split over this case, the government now appears to have decided to adopt the position taken by the Catholic Church, our correspondent adds.
Senior Vatican officials have, in recent months, described attempts to stop feeding Ms Englaro as euthanasia. One cardinal said it amounted to murder.
On Sunday, Pope Benedict XVI added his voice to the debate about euthanasia, calling it a "false solution" to the tragedy of suffering.