She's the most high-profile guest of the "Katholikentag," Germany's Catholic Convention: Chancellor Angela Merkel came to the five-day event in Münster as it turned its attention to international politics on Friday.

Merkel called the US decision to leave the Iran nuclear deal "a cause of great concern," in a panel discussion and emphasized the role of international cooperation when confronting crises.

"If we always step away from multilateral agreements as soon as we don't like something about them, that would be a bad message for the world. We want to strengthen multilateralism," the chancellor said.

Read more: Germany reaffirms Iran nuclear deal but business worries abound

She said the US decision was a "serious incident" but not a reason to call the entire transatlantic relationship into question, adding that she would "continue to support transatlantic partnership."

Stop mopping water and turn off the tap

The number of asylum-seekers arriving in Europe was another major point of discussion for the panel, moderated by DW journalist Astrid Prange de Oliveira.

Merkel has come under criticism for a refugee policy that some conservatives call too generous and how best to integrate, support or expel asylum-seekers continues to divide many in Germany.

Read more: German academics propose new approach to immigration reform

Cardinal Peter Turkson, a prefect in the Vatican Dicastery for Promoting Integral Human Development, said he appreciated what Germany and the European Union had done in recent years, how they accepted people fleeing war and destruction and promoted integration.

He also stressed that there was more to be done.

"We also need to help refugees' home countries," and improve conditions there, Turkson said. "Right now, Europe is mopping up water, but we need to turn off the tap! Or we'll be forever mopping up water."

Asked when Germans could expect the long-discussed immigration law that would clarify legal paths of migration and the numbers in which immigrants could enter Germany, Merkel replied it was a priority.

"We will have an immigration law in two years time," she added. "Maybe sooner."

Peace from the ground up

Tilman Brück, a senior fellow at the Stockholm International Peace Research Institute, pointed out the importance of maintaining dialogue with countries whose leaders could be difficult.

"Peace is not only brought about from the top down," Brück said. "It can also come from the ground, from the population. That's why dialogues for peace should also include efforts to improve people's lives, giving them hope and ensuring, for example, that their kids can go to school."

Candid message on arms exports

Merkel talked about a more contentious way of promoting peace: arms exports. She said in some cases it would be essential to support the fight against terrorism not just by training soldiers, but also by sending weapons — a position not exactly popular with many Germans, especially Christians, Merkel acknowledged.

Merkel explained why the German government supplied the Kurdish Peshmerga fighters with weapons, for example.

"You have to think this through to the end. When terrorists have Kalashnikovs, should we train the soldiers fighting against them but then say, 'You're on your own' when it comes to weapons?'" the chancellor asked. "You have got to be honest" and realize that it doesn't work like that, Merkel added.

Read more: Germany quintuples arms sales to Saudi Arabia and Egypt

While arms exports remain a contentious issue in Germany, at least the audience at the 101st Catholic Convention seemed to agree with Merkel. Her statements were met with long applause at the conference taking place with "seek peace" as its overarching theme.