America's commitment to Nato is "unwavering", US Vice President Mike Pence has said.
In his first foreign trip as vice president, Mr Pence sought to address concerns raised by President Donald Trump's earlier comments questioning whether Nato was "obsolete".
Mr Pence told the Munich Security Conference, an annual gathering of diplomats and defence officials: "I bring you this assurance - the United States of America strongly supports Nato and will be unwavering in our commitment to our trans-Atlantic alliance."
"Your struggles are our struggles. Your success is our success," Mr Pence said. "And ultimately, we walk into the future together."
German Chancellor Angela Merkel, speaking before Mr Pence, told him and other leaders that "acting together strengthens everyone".
Her address came amid concerns among allies about the Trump administration's approach to international affairs and fears that the US may have little interest in working in international forums.
"Will we be able to continue working well together, or will we all fall back into our individual roles?" Mrs Merkel asked. "Let's make the world better together and then things will get better for every single one of us."
Mr Trump has praised Britain's decision to leave the 28-nation EU, and a leading contender to be the next US ambassador to the EU, Ted Malloch, has said Washington is "somewhat critical and suspicious" of the bloc and would prefer to work with countries bilaterally.
Mr Pence did not mention the European Union in his speech, something picked up on by French Foreign Minister Jean-Marc Ayrault who wrote on Twitter: "In Munich, Vice President Pence renews America's commitment to the Atlantic alliance. But not a word on the EU."
Mr Pence did say, however, that the US was on a path of "friendship with Europe and a strong North Atlantic alliance".
German Foreign Minister Sigmar Gabriel also indicated scepticism about Mr Pence's pledges, saying that he agreed Europe needed to work with the US on the basis of common values.
But in a barely veiled reference to Mr Trump, he said "both countries must define their interests, and our foreign policies should not be driven by ideology.
"Ideologies lead to hostile concepts that might not be able to be overcome," said Mr Gabriel, who is chairman of the Social Democratic Party, Mrs Merkel's junior coalition partner.
He said Europeans "should hope for the best, but prepare for the worst".
In pledging the Trump administration's support for Nato, Mr Pence said the US expected all countries to live up to commitments to spend at least 2% of gross domestic product spending on defence.
"Europe's defence requires your commitment as much as ours," he said.
Mrs Merkel reiterated that Germany is committed to the 2% goal though Germany currently only contributes about 1.3%.
"We will do everything we can in order to fulfill this commitment," she said. "But let me add, however, that I believe while Nato is very much in the European interest, it's also in the American interest - it's a very strong alliance where we are united together."
Mr Gabriel suggested that development aid and humanitarian moves - such as in Germany's decision to take in nearly 900,000 refugees last year - should also be part of the consideration when looking at defence spending.
NATO Secretary General Jens Stoltenberg told The Associated Press, however, that both things were necessary.
"We need a comprehensive approach and of course development aid and funding for refugees is also very important," he said. "But there's no contradiction between being focused on development aid and security - actually the only way we can create development is to preserve the peace. We need security to be able to facilitate economic development."
US Homeland Security Secretary John Kelly told the security conference that Mr Trump is working on a "streamlined" version of his executive order banning travel from seven predominantly Muslim nations to iron out the difficulties that landed his first order in the courts.
Mr Kelly said that next time Mr Trump will "make sure that there's no one caught in the system of moving from overseas to our airports" during the travel ban.
The nations affected by the original ban were Iran, Iraq, Libya, Somalia, Sudan, Syria and Yemen. Mr Kelly mentioned "seven nations" again on Saturday, leading to speculation they will all be included in Mr Trump's next executive order on immigration.