German Chancellor Angela Merkel has said Islam is not the source of "terrorism" and that cooperating with predominantly Muslim states in the fight against it is vital.

Merkel, who has been critical of US President Donald Trump's attempt to impose a temporary travel ban on people from seven Muslim-majority countries, was speaking on Saturday at the Munich Security Conference, with US Vice President Mike Pence in the audience.

"I think, those countries, first and foremost have to give a contribution. Because only in this way we would be able to convince people that it is not Islam that is the source of terrorism. But a falsely understood Islam," she said.

"I expect from religious authorities of Islam to find strong language in order to delimitate peaceful Islam from terrorism committed in the name of Islam. We as non-Muslims cannot do this, it should be done by Islamic clergy and authorities," she added.

Merkel said Europe's ties with Russia remained challenging, but it was important to work with Russia in the fight against the Islamic State of Iraq and the Levant (ISIL, known as ISIS) and similar groups.

She stressed the need to preserve and strengthen multilateral structures such as the EU, NATO and the UN during an address that came as concern grew about the Trump administration's approach to international affairs and fears that it may have little interest in working in multilateral forums.

Trump's criticism of NATO as "obsolete", his praise for Britain's decision to leave the EU as well as his softer approach towards Russia have unnerved allies.

"Acting together strengthens everyone," said Merkel. "We must see that the multilateral structures are in many places not efficient enough.

"I am firmly convinced that it is worth fighting for our common international multilateral structures, but we must improve them in many places."

Pence reassures watchful allies

Pence, though, in his first overseas trip since being named vice president, said Trump would stand by NATO and no one should doubt his commitment after the sacrifices made to defend it.

"The president asked me to be here today to convey a message, a reassurance - the US strongly supports NATO and we will be unwavering in our commitment to this transatlantic alliance," Pence said. "Let no one doubt our commitment."

READ MORE: Donald Trump 'committed to NATO'

Al Jazeera's Dominic Kane, reporting from the conference, said many people had wanted to hear Pence speak as speculation grew about Trump's approach to foreign policy.

"Delegates here will be discussing the future of NATO as well as the future of the West," Kane said. "With all these leaders speaking, it shows how important the conference has become in recent time.

"The fact that Merkel spoke about ISIL and Boko Haram and the need to consign these people to history shows leaders here are in earnest about how they deal with the problem.

"The question is though what policy will emerge from this. Is it likely this conference will arrive at a meaningful policy which will deal with these groups? That's a much more difficult question to answer."

Pence is also scheduled to sit down with the leaders of the Baltic States of Estonia, Latvia and Lithuania and Ukrainian President Petro Poroshenko - all countries dealing with the threat of Russian incursion - along with Turkey's prime minister, Binali Yildirim.