The Vatican (LifeNews.com) -- In a Sunday speech that is his first on pro-life issues, newly-elected Pope Benedict XVI said he has no plans to change the Catholic Church's long-held pro-life stance against abortion and euthanasia. He said church leaders must resist the urge to "water down" Catholic teachings on the important issues.

A pope "must not proclaim his own ideas, but ever link himself and the church to obedience to the word of God, when faced with all attempts of adaptation or of watering down, as with all opportunism," Benedict said.

"That's what Pope John Paul II did, when ... faced with erroneous interpretations of freedom, underlined in an unequivocal way, the inviolability of human beings, the inviolability of human life from conception to natural death," Pope Benedict said.

"The freedom to kill is not a real freedom, but a tyranny that reduces the human being to slavery," he added, clearly condemning practices such as assisted suicide and embryonic stem cell research.

His words were met with loud cheers and applause.

"The pope isn't an absolute sovereign, whose thoughts and desires are law," Benedict said. "On the contrary, the ministry of the pope is the guarantor of the obedience toward Christ and his word."

The pontiff also said is job was to ensure that important Catholic pro-life doctrine was not "shattered by constant changes in fashion."

Pro-life organizations celebrated when the former Cardinal Joseph Ratzinger was named the head of the Catholic Church because of his strong pro-life views as the director of the office of Catholic teachings under Pope John Paul II.

"For decades, he has been a strong voice in favor of life, clearly articulating the Church's teachings," Father Frank Pavone, the director of Priests for Life, said of Pope Benedict.