The court had been scheduled to rule on a 2005 petition by then-Attorney General Claudio Fontelles, who argued that a law passed that same year allowing embryonic stem cell research was unconstitutional because it violates the right to life.

The law opened the way for research with embryos resulting from in-vitro fertilization that have been frozen for at least three years.

The session was suspended, almost five hours after it began, when Justice Carlos Alberto Menezes Direito formally requested more time to consider the issue. He has 10 to 30 days to present his opinion during another session, according to the court's press office.

Before the adjournment, current Attorney General Antonio Fernando Souza and a lawyer for Brazil's Roman Catholic Church argued that embryonic stem cell research should be banned because the process involves destroying embryos, which they said ends human life.

Other attorneys representing the government and Congress defended the 2005 law, saying research with embryonic stem cells could lead to cures of diseases such as Parkinson's, multiple sclerosis and diabetes.

While embryonic stem cell research is currently legal, scientists have put most projects on the back burner pending the Supreme Court's ruling.