Secretary of State John Kerry, right, speaks with Iranian Foreign Minister Mohammad Javad Zarif, left, as they walk in the city of Geneva, Switzerland, on Jan. 14, 2015, during a bilateral meeting ahead of the next round of nuclear discussions. (Martial Trezzini/AP)

Iranian Foreign Minister Mohammad Javad Zarif expressed concern Wednesday about “extremely dangerous” anti-Muslim demonstrations taking place in Europe and called for people’s beliefs to be respected in the wake of last week’s massacre at the offices of a Paris newspaper.

Zarif spoke to reporters before he and U.S. Secretary of State John F. Kerry met four times, for a total of about six hours, to discuss protracted negotiations on curbing Iran’s nuclear capacity.

Zarif and Kerry plan to attend the World Economic Forum in Davos, Switzerland, next week and are expected to talk again there.

The five permanent members of the U.N. Security Council plus Germany, known collectively as the P5+1, are trying to negotiate a deal with Iran that would effectively block its ability to enrich uranium to weapons-grade levels. In return, Iran wants Western sanctions lifted, or at least eased.

The talks have dragged on for more than a year with no resolution, and deadlines have been extended twice. Now negotiators face a June 30 deadline, although Kerry has said that if there is no visible progress by March, negotiators will have to reconsider whether there is any point in continuing.

“That’s why we’re here,” Zarif said when asked whether he was optimistic about progress.

As he awaited Kerry’s arrival for the first of several meetings Wednesday, reporters peppered Zarif with questions, which he answered in an affable manner as he explained the policies of a regime that the United States suspects wants to acquire the ability to build nuclear weapons. He adopted a reasonable tone when discussing a cartoon of the prophet Muhammad published Wednesday in the Parisian satirical newspaper Charlie Hebdo, musing that the world would be a nicer place if everyone respected everyone else’s opinion.

“We believe that sanctities need to be respected,” Zarif said. “And unless we learn to respect one another, it will be very difficult in a world of different views and different cultures and civilizations. We won’t be able to engage in a serious dialogue if we start disrespecting each other’s values and sanctities.”

He added: “I think you would agree we would have a much safer, much more prudent world if we were to engage in serious dialogue, serious debate about our differences. And then we will find out that what binds us together is far greater than what divides us.”

Charlie Hebdo displayed the cartoon on the cover of the first issue published since two masked and heavily armed Islamist militants assaulted its offices a week ago, killing 12 people in France’s deadliest terrorist attack in decades. A gunman who sympathized with the two attackers killed a Paris policewoman last Thursday and four Jewish hostages at a kosher grocery store Friday. All three gunmen died in police raids Friday.

Expressing concern about anti-Muslim demonstrations in Europe, Zarif said the problems of extremism are “very serious,” both in the Middle East and in Europe.

“You’ve seen demonstrations here in Europe which are extremely dangerous,” he said. “And we need to see a way to deal with this.”

Asked about Washington Post reporter Jason Rezaian, who has been imprisoned in Tehran on unspecified charges for more than five months without access to a lawyer, Zarif said the government is doing its best to provide “humanitarian assistance” while the case is before a court. But he made clear that there was little he could do about the situation.

Nuclear talks involving the United States, the European Union and Iran will continue through Saturday. Negotiators from the P5+1 nations and Iran are scheduled to begin discussions Sunday.

Both the Iranian and the U.S. governments face an uphill battle at home because of opposition to a deal.

Some members of Congress, both Democrats and Republicans, want to impose more sanctions, a step that some experts warn could spur Iran to resume enriching uranium free of the limits it accepted in a temporary pact.

And in Iran, President Hassan Rouhani faces hard-liners who are wary of dealing with the United States, which they consider an implacable enemy. In a Jan. 4 speech, Rouhani, an Iranian moderate, took them on directly.

“Our ideals are not bound to centrifuges,” Rouhani said, referring to the uranium-enriching machines whose numbers the P5+1 nations want Iran to pare significantly. He also proposed a referendum on the issue.

A few days later, Iran’s supreme leader, Ayatollah Ali Khamenei, expressed skepticism about the talks, even though he did not oppose them outright. He said that the United States could not be trusted to lift sanctions and that “efforts must be made to immunize Iran against the sanctions.”

The discussions in Geneva are supposed to lay out a framework for more talks, and no breakthrough is expected.

Nonetheless, Zarif called his talks with Kerry on Wednesday an “important” step.

“I think it will show the readiness of the two parties to move forward, to speed up the process,” he said.

The questioning of Zarif stopped with the arrival of Kerry, whom Zarif dubbed a “wise” man for being a little late. Kerry declined to comment on the talks.

Earlier, Kerry met with Staffan de Mistura, the U.N. special envoy for Syria. Kerry expressed support for Russian efforts to forge a peace deal after almost four years of war that has displaced nearly three-quarters of the country’s population and flooded neighboring nations with refugees.

Russia has proposed holding a meeting in Moscow this month with representatives of Syrian President Bashar al-Assad’s government and members of the opposition.

Kerry called the war in Syria a “continued catastrophe.” The conflict has galvanized Islamist militants around the world, inspiring them to join extremist groups battling Assad’s forces.

“It is time for President Assad, the Assad regime, to put their people first and to think about the consequences of their actions, which are attracting more and more terrorists to Syria, basically because of their efforts to remove Assad,” Kerry said.

William Branigin in Washington contributed to this report.