BRUSSELS (AP) — U.S. Secretary of State Marco Rubio and the Trump administration’s new envoy to NATO arrived Thursday in Brussels, where the alliance’s top diplomats are hoping they’ll shed light on U.S. security plans in Europe.

European allies and Canada are deeply concerned by President Donald Trump’s readiness to draw closer to Russian leader Vladimir Putin, who sees NATO as a threat, as the U.S. works to broker a ceasefire in Ukraine.

Recent White House comments and insults directed at NATO allies Canada and Denmark — as well as the military alliance itself — have raised alarm and confusion, especially with new U.S. tariffs targeting U.S. friends and foes alike.

Since Defense Secretary Pete Hegseth warned last month that U.S. security priorities lie elsewhere — in Asia and on the U.S.'s own borders — the Europeans have waited to learn how big a military drawdown in Europe could be and how fast it may happen.

In Europe and Canada, governments are working on “burden shifting” plans to take over more of the load, while trying to ensure that no security vacuum is created if U.S. troops and equipment are withdrawn from the continent.

These allies are keen to hear from Rubio what the Trump administration’s intentions are and hope to secure some kind of roadmap that lays out what will happen next and when, so they can synchronize planning and use European forces to plug any gaps.

In a statement, newly confirmed U.S. ambassador to NATO Matt Whitaker said that “under President Trump’s leadership, NATO will be stronger and more effective than ever before, and I believe that a robust NATO can continue to serve as a bedrock of peace and prosperity.”

But he added: “NATO’s vitality rests on every ally doing their fair share.”

Whitaker affirmed the U.S. commitment to NATO’s collective security guarantee, which says that an attack on any ally must be considered an attack on them all, but that his brief would also be to encourage Europe to lead on “peace, security, and the rebuilding of Ukraine.”

The statement said allies should demonstrate that NATO takes seriously threats from China.