US vice-president to explain Trump's vision to foreign leaders, allies

US Vice-President Mike Pence heads to Europe this week to meet with allies seeking clarity on the Trump administration's foreign policy strategy and its stance toward Russia after the resignation of the top White House national security aide.

Pence, who has hewn more closely to Republican orthodoxy than his boss President Donald Trump, will attend the Munich Security Conference this weekend and will visit Brussels.

The trip comes as turmoil swirls within the administration following the resignation of Trump's national security adviser, Michael Flynn, on Monday.

Flynn, who championed closer ties to Russia, stepped down after reports he had discussed US sanctions on Moscow with Russia's ambassador.

Even before Flynn's departure, Trump's calls for warmer ties with Moscow and his praise of Russian President Vladimir Putin had unnerved both US lawmakers at home and NATO allies.

Trump has called NATO "obsolete" and said member nations were not paying their fair share for US protection.

Some European capitals greeted Flynn's departure with relief. Flynn was seen by some officials in Europe as one of the Trump administration's leading advocates of closer ties to Russia and a hardline opponent of the 2015 nuclear deal between Iran and western powers.

One fear, ahead of a series of important elections in Europe, is that a Trump White House could actively promote the disintegration of the European Union, Wolfgang Ischinger, chairman of the Munich Security Conference told reporters in Berlin.

Ischinger said he hopes Pence states clearly that the breakup of the EU is not the goal of the US government.

"I think from the administration's point of view, this is an opportunity to make a very major pronouncement on its foreign policy and its European policy," said Alexander Vershbow, a former US ambassador to Russia and a former deputy secretary general of NATO.

The White House has not yet previewed Pence's remarks.

Pence's comments on Russia's incursions into Ukraine will be closely parsed to see whether Trump will be willing to trade off US economic sanctions to achieve other security goals, said Vershbow, now with the Atlantic Council.

Trump's mixed messages on NATO have perplexed European allies.

"One minute NATO is obsolete - the next minute he loves NATO. One minute NATO is an impediment and doesn't do anything for terrorism - the next minute NATO is the centerpiece of the global fight," said retired US Navy Admiral James Stavridis, a former supreme allied commander of NATO.

Pence is the right person to set a more reassuring tone, said Stavridis, now dean of the Fletcher School of Law and Diplomacy at Tufts University.

"Because of his personality: he's calm, he's centered, he's thoughtful, he's widely regarded with respect on both sides of the aisle in the United States," Stavridis said in an interview.

With Flynn's departure, European officials said they hope Pence, Defense Secretary James Mattis and Secretary of State Rex Tillerson become the dominant players in Trump's foreign policy. But this remains an open question.

Tillerson is also in Europe this week, meeting with G20 nations in Bonn, and Mattis traveled to NATO, warning allies that they must honor military spending pledges.

German Defence Minister Ursula von der Leyen said on Wednesday she could understand the US call for NATO partners to step up funding for the transatlantic alliance and European allies would meet their obligations "in the coming years".

The United States for years has called for European allies to spend 2 percent of their economic output on defence.

"We Europeans, we Germans, we have to do more for our own security, we have to invest more there," Leyen told ARD public television.

She said it was "really not fair" that the US was doing twice as much for security than all European countries together.

"So in this respect, the Americans are right when they would like to hear from us how we show convincingly how we can meet the 2-percent-goal in the NATO in the coming years," she said.