MUNICH — Bearing what he said was a message from President Trump, Vice President Mike Pence told anxious European political and security leaders Saturday that “the United States of America strongly supports NATO and will be unwavering in our commitment to this trans-Atlantic alliance.’’

But while offering that assurance to European partners alarmed by Trump’s rise, along with some tough words on Russia and Ukraine, Pence also warned that Europe must increase its military spending in a dangerous world, saying, “As you keep faith with us, under President Trump, we will always keep faith with you.’’

The NATO treaty demands not only collective defense but also a vow to “contribute our fair share to our common defense,’’ Pence, making his first overseas trip as vice president, said at an annual security conference in Munich.

“That pledge has gone unfulfilled for too many for too long, and erodes the very foundation of our alliance,’’ Pence said. He echoed an early theme of Trump, who has said he believes that the United States’ allies have taken advantage of US largesse and not paid their fair share.

“Europe’s defense requires your commitment as much as ours,’’ Pence said.

NATO allies have promised to reach the goal of spending 2 percent of gross domestic product on defense by 2024, but only five countries meet that figure. Germany, for instance, which has Europe’s largest economy, spends only 1.2 percent of GDP on its military, though it increased spending 8 percent last year.

Pence said pointedly that while some NATO members met the spending goal, “many others, including some of our largest allies, still lack a credible path.’’ Trump, he said, “expects allies to meet that goal. For most, that means the time has come to do more.’’

Applause for Pence’s speech was thin. Chancellor Angela Merkel of Germany, who spoke before the vice president, argued that increases in military spending must be gradual to be efficient and effective.

Merkel said that spending on other matters — like development aid, education for girls and women, and caring for refugees — also contributes to mutual security, as do stronger multilateral institutions like the European Union and the United Nations, which Trump has criticized.

Europe needs the support of the United States in the face of Islamist terrorism and Russian ambition, Merkel said, promising to continue to spend more to meet NATO goals. “We need the military strength of the United States,’’ she said.

But she warned against nationalism, without specifically naming Trump’s “America First’’ idea. “Will we be able to continue working well together, or will we all fall back into our individual roles?’’ she asked. “Let’s make the world better together, and then it will be better for each of us.’’

Merkel is facing a reelection campaign in September in which the extent of increased military spending is a hot issue, as is her handling of the influx of refugees into Europe.

Pence’s message, which was similar to that offered in Munich last week by Defense Secretary Jim Mattis, appeared to have done little to reassure Europeans who think that making NATO commitments conditional on spending undermines the credibility and deterrence of the alliance.

“American government officials need to go back to Washington recognizing that there are serious concerns in Europe, especially in Germany, about a host of issues, from trade to foreign policy and NATO,’’ said Steven E. Sokol, president of the American Council on Germany.

“Even though they gave reassurance, people here will hold them to it, and it will make matters worse if these reassurances just pay lip service to those concerns and make it that much harder to rebuild trust in what is an indispensable partnership,’’ he said.

Strobe Talbott, president of the Brookings Institution in Washington, said Pence had accomplished his main task by conveying the administration’s commitment to NATO. “It had the big reassurance,’’ Talbott said. “He made clear he was speaking for the president.’’

Thierry de Montbrial, executive chairman of the French Institute of International Relations, said Pence had done a good job of “delivering the gospel that people needed of the importance of the trans-Atlantic alliance.’’

A senior White House foreign policy adviser said Pence wanted to send a message of reassurance as well as obligation, both in Munich and in Brussels, where he will meet with EU and NATO officials Monday.

It included strong words on Russia, even as Europeans wonder about the admiration Trump has shown for President Vladimir Putin of Russia.

Pence vowed that the United States would “hold Russia accountable, even as we search for new common ground which, as you know, President Trump believes can be found.’’