NATO Secretary-General Mark Rutte on Tuesday brushed aside fresh concerns about the United States' commitment to the military alliance ahead of a meeting of allied foreign ministers focused on the war in Ukraine.

U.S. Secretary of State Marco Rubio was expected to miss Wednesday's gathering in Brussels, which will take place during high-stakes negotiations in Moscow and elsewhere in Europe about Ukraine's future. The rare absence of America's top diplomat at the U.S.-led alliance comes after President Donald Trump's 28-point peace proposal dismayed European allies and Canada last month.

Rutte told reporters he would "not read anything" into Rubio's decision to skip the meeting.

"He's working extremely hard to take care not only of the situation of Ukraine, but of course many other issues which are on his plate," Rutte said. "So I totally accept him not being able to be here tomorrow, and I would not read anything in it."

A senior State Department official, speaking on condition of anonymity to discuss the internal administration reasoning for the absence, said Rubio has already attended dozens of meetings with NATO allies, "and it would be completely impractical to expect him at every meeting."

Deputy Secretary of State Christopher Landau will attend in Rubio's place and press the allies to deliver on their commitment to invest 5% of gross domestic product on defense.

European concerns over Trump peace plan

The Trump administration's draft plan to end the nearly four-year war suggested that NATO would not expand further and that Ukraine would not be admitted to the alliance. Both points represent longtime Russian demands. The proposal would break with a years-long promise to Kyiv that it has a place at the organization's table.

The plan also stated that a dialogue would be held between Russia and NATO, mediated by the United States, to resolve all security issues and create business opportunities. It remains unclear how NATO's most influential member might serve as an impartial mediator between the alliance and Moscow.

Rutte downplayed the contentious elements of Trump's original plan, saying it has been heavily reworked to address European concerns.

"You need to start somewhere. You need to have proposals on the table," he said.

Rutte added that NATO-specific elements of any deal to end the war "will be dealt with separately. And that obviously will include NATO."

At a pivotal moment in the alliance's history, European allies see Russia's invasion of Ukraine as an existential threat. Senior officials have warned that Russian President Vladimir Putin might launch another attack on Europe within three to five years should he prevail in Ukraine.

At the same time, the United States has insisted that its allies must take care of security in their own backyard. Doubts about America's NATO leadership and the alliance's unity could undermine the organization's ability to deter an adversary like Putin.

Ukraine membership remains in limbo

Despite the proposal to rule out Ukrainian membership, Rutte insisted that the country remains on an "irreversible path" to join the world's biggest security organization, as NATO leaders pledged at their Washington summit in 2024.

But the former Dutch prime minister acknowledged that Ukrainian membership is politically impossible at present. Admission would require the unanimous agreement of all 32 allies. The Trump administration has ruled out Ukraine's membership, and Hungary and Slovakia are also opposed.

"Right now, as you know, there is no consensus on Ukraine joining NATO," Rutte said.

The lack of consensus leaves Ukraine in a precarious position. Kyiv has sought NATO membership as a security guarantee against future Russian aggression. Without that protection, any peace deal would leave Ukraine reliant on other forms of security assurances that critics argue would be difficult to enforce.

Mixed signals from Trump

President Trump provided reassurance to European partners at NATO's last summit in The Hague when he affirmed the U.S. commitment to Article 5, the collective security guarantee that says an attack on any ally should be considered an attack on all of them.

Trump described the other NATO leaders as a "nice group of people" and said that "almost every one of them said 'Thank God for the United States.'"

But several of his remarks since then have appeared to place the United States outside the organization it has long led.

"We're selling a lot of weapons to NATO, and that's going, I guess, to Ukraine for the most part," Trump said at a White House meeting with Finnish President Alexander Stubb in October. "That's up to them, but they're buying weapons from the U.S."

The framing positioned the United States as a weapons supplier to NATO rather than as the alliance's leading member. European officials have noted the distinction in private conversations, according to diplomats familiar with the discussions.

Troop drawdown adds to uncertainty

Concerns are also high about a further U.S. troop drawdown in Europe. Romania announced in October that the United States would reduce its military presence in the country by up to 3,000 troops as Washington focuses on security threats in Asia and elsewhere.

The administration is expected to announce its broader troop movement plans in early 2026.

The potential reduction comes as NATO allies along the alliance's eastern flank have sought greater U.S. military presence to deter Russian aggression. Poland, the Baltic states, and Romania have all pressed for additional American forces since Russia's full-scale invasion of Ukraine in February 2022.

Rutte has repeatedly urged allies to increase their own defense spending and capabilities to reduce dependence on American military power. The push for 5% of GDP on defense represents a significant increase from the current 2% target that many NATO members have only recently met.

Wednesday's foreign ministers meeting will focus on how to sustain support for Ukraine as peace negotiations continue. Special envoy Steve Witkoff is scheduled to meet with Putin in Moscow this week to present a revised version of Trump's peace plan.

The outcome of those talks could determine the shape of any settlement and, by extension, the future security architecture of Europe. For now, Rutte's message to allies is to stay focused on the immediate task at hand.

"When it comes to the NATO elements of a deal to end the war against Ukraine, that will be dealt with separately," he said. "And that obviously will include NATO."