Rex Tillerson's inaugural welcome at NATO headquarters Friday may have been slightly less hearty than could otherwise have been expected after the US Secretary of State initially expressed his willingness to entirely skip the get-together, originally scheduled for next week. That tension, coupled with ongoing US pressure to boost defense budgets faster than agreed, has fueled an unending stream of speculation over if and how Tillerson would tweak the standing talking points.

The top US diplomat started out by being reassuring. "Let me be very clear at the outset of my remarks," he told allies, "the US commitment to NATO is strong and this alliance remains the bedrock for transatlantic security." He tipped his hat to concerns sparked by President Donald Trump about the fallibility of Article 5 - the pledge for collective defense. "We understand that a threat against one of us is a threat against all of us, and we will respond accordingly," Tillerson went on. "We will uphold the agreements we have made to defend our allies." A practical example of that, he noted, is the fact that a US battalion arrives in Poland Saturday to lead one of four battle groups serving as a deterrent against what Tillerson called "Russian agitation and Russian aggression."

Make money plans by May

But then he launched into the financial argument everyone knew was coming: "It is no longer sustainable for the US to maintain a disproportionate share of NATO's defense expenditures." Tillerson said Washington wants to see "national plans" by the end of the year from each ally. The plans would detail countries' cash contributions along with other capabilities, as well as progress toward the agreed goal of spending 2 percent of GDP on defense, formalized at the 2014 Wales summit.

Some NATO sources said the mood in the room was generally positive and broadly supportive. But expectations that all would go Washington's way were rent asunder by German Foreign Minister Sigmar Gabriel, who arrived at the gathering saying bluntly that Germany has no intention of meeting the 2 percent goal. "I don't know a politician in Germany who believes that this would be achievable or even desirable," Gabriel said.

He added that Germany already has a "national plan" - "it's called the budget," he quipped.

German Foreign Minister Sigmar Gabriel suggested NATO's spending target of 2 percent is not mandatory

Kristine Berzina, a foreign policy analyst at the German Marshall Fund in Brussels, said despite all the angst over having to reschedule 27 ministers to accommodate the US, it was worthwhile given the magnitude of the question on the table that dwarfs the individual items on the agenda: will the US maintain its leadership role within the alliance? NATO allies need to know, Berzina said, "and they are willing to accommodate their schedule in order to obtain that answer." She added that "there are questions around Brussels about whether the scheduling issue is something we'll see more of ... part of a broader trend prioritizing bilateral relations or multilateral frameworks?"

Before coming to Brussels, Tillerson made a visit to Turkey; he had initially announced he would go to Moscow despite missing the NATO ministerial meeting.

NATO Secretary-General Jens Stoltenberg, who has supported the Trump rhetoric as a way to reinforce his own long fight to boost spending, nonetheless issued a defense of European contributions. "Two World Wars and the Cold War have taught us all that stability in Europe is of course important for Europe, but it's also important for the United States," he said, "and the only time we have invoked Article 5 was after the attack on the United States. Hundreds of thousands of European soldiers and other partner nations have served in Afghanistan alongside US soldiers, and more than a thousand have lost their lives in Afghanistan in an operation which was a direct response to an attack on the United States."

Former British Ambassador to NATO Sir Adam Thomson, now with the London-based European Leadership Network, thinks the alliance should continue making its own case to Washington. "NATO will and does actually have a rather good story to tell about how much it has contributed, including supporting the United States in its response to 9/11, the longest war in US history in Afghanistan, the training in Iraq," he told DW. But at the same time, Thomson acknowledged a supporting role wouldn't cut it if push came to shove and massive military might was needed. "Europeans on their own probably couldn't provide for the collective defense of their territories at the levels that NATO believes is necessary," he said.

Decade-long demand

Former Estonian President Toomas Ilves says no one should be surprised this issue is central to the new US leadership, pointing out it has been percolating for a decade. Estonia is well above the 2 percent spending mark, one of only five countries at present. Ilves recalled the stark message delivered in Brussels by outgoing US Defense Secretary Robert Gates in 2011, in which he said NATO would face a "dim if not dismal future” without increased European funding. "He said the American people and their elected representatives are not going to stand for this for too long," Ilves explained. "So here we are seven years later."

So why is the atmosphere so toxic now? Thomson's theory is that it's all about the delivery. "The Obama administration knows how to do diplomacy," he said, "and the Trump administration hasn't learned that yet."