In his historic 2001 visit to Syria, John Paul II became the first pope to visit a mosque, where he stressed the common heritage of Christianity and Islam and highlighted the prominence of the Virgin Mary in the Koran. He also noted a certain "misuse [of] religion itself to promote or justify hatred and violence" but left it undefined.

But when John Paul's successor, Pope Benedict XVI, met with Muslim leaders in Cologne, Germany, last Saturday, he stuck to one issue and gave it a name -- terrorism.

With a challenge to Muslim leaders to reject and condemn "any connection between your faith and terrorism," Benedict has subtly redefined Vatican relations with Islam, departing from the conciliatory overtures of his predecessor to forge an approach that presses for reform.

The shift, observers say, reflects a growing desire among Vatican officials for the Catholic Church to reassert itself after two decades of dovish dialogue under John Paul II.

Support for interreligious dialogue remains strong, but the growth of European Islam and a declining Christian presence in predominantly Muslim countries -- coupled with the spread of Islamic terrorism -- has prompted a new Catholic consensus that conditions must be placed on future contact.

"We have to be very blunt and not hide behind formulas," said the Rev. Justo Lacuna Balda, president of the Pontifical Institute for Islamic and Arab Studies, a Vatican think tank. Benedict "has indirectly said, 'You've got people in your midst who are saying let's fight against the West and let's fight against Christians and Jews. Well, wait a minute. Where do they get this from? Who teaches them this?' "

Although Benedict stopped short of directly linking terrorism with Islam, the pope for the first time called on Islamic leaders to reject interpretations of Islam that inspire terrorism.

"Words are highly influential in the education of the mind. You therefore have a great responsibility for the formation of the younger generation," the pope said. "There is no room for apathy and disengagement, and even less for partiality and sectarianism."

The address prompted Corriere della Sera, Italy's largest newspaper, to proclaim in an editorial, "Finally there's a pope that condemns Islamic terrorism in front of a Muslim delegation without if's, and's or but's."

Under John Paul, dialogue with Islam focused on the faiths' common historical roots and mutual emphasis on sexual morality. Divisive topics such as terrorism or discrimination against Christians were sidelined.

When condemning terrorism, the late pope usually minimized religious references and always excluded any direct mention of Islam. Many say this policy was driven by concerns that tough talk from the Vatican might signal a "clash of civilizations."

"The objective was to ward off a greatly feared clash by coming together," said Sandro Magister, a veteran Vatican analyst for Italy's L'espresso magazine. Magister described John Paul's outreach as an indiscriminate "tendency to hug" Muslim leadership.

As recently as 2004, high-level Vatican officials attended talks in Qatar that included Sheik Yusuf al-Qaradawi, founder of the European Council for Fatwa and Research (ECFR), and other radical clerics. In recent years the ECFR, a religious authority for European Muslims, has issued fatwas supporting suicide attacks in Israel and corporal mutilation in Iraq.

"In Cologne, Benedict XVI demonstrated a different vision, discriminating between positive dialogue and dialogue that is unacceptable," Magister said.

Balda said discussions with controversial leaders will have to be discreet. "The high-level meetings behind closed doors will continue, but we cannot give a platform to people who create animosity and division."

Muslims who met with the pope in Cologne were drawn from groups representing moderate Islam. Some praised his focus on terrorism, while others called for the dialogue to be extended to issues ranging from poverty and globalization to whether Turkey should be admitted to the European Union.

As Cardinal Joseph Ratzinger, Benedict expressed opposition to Turkey's bid in a 2004 magazine interview on the grounds that the country's Islamic identity clashed with Europe's Christian roots.

Many inside the Vatican see Turkey's push for EU membership as symptomatic of a lack of "reciprocity" between Islam and Christianity. Turkey fails to guarantee the rights of religious minorities, Balda said, limiting the possibility for Christian minorities to flourish there. At the same time, Turkey's entrance into the EU would establish a European beachhead for Islam, altering the EU's religious demographics.

"You cannot expect that on this side of the border you as a Muslim will have the right to practice your religion and I as a Buddhist or as a Christian will not have exactly the same welcoming on your side," Balda said. "This is a vital question that needs to be brought to the forefront of interreligious dialogue."

In Cologne, Benedict appeared to underline this disparity when he called for more religious tolerance.

"We must seek paths of reconciliation and learn to live with respect for each other's identity," he said. "The defense of religious freedom, in this sense, is a permanent imperative and respect for minorities is a clear sign of true civilization."

As a cardinal, however, Ratzinger expressed doubts as to whether such reconciliation is possible. "Islam has a total organization of life that is completely different from ours," he said in a 1997 interview.

"There is a very marked subordination of woman to man; there is a very tightly knit criminal law, indeed, a law regulating all areas of life, that is opposed to our modern ideas about society."

Pope Benedict XVI talks with Elyas Nadeem, chairman of the Central Council of Muslims in Germany, as he receives delegates of Muslim communities last Saturday in Cologne.