While meeting with NATO leaders in Brussels, American Secretary of Defense James Mattis once again called on member nations to fulfill their financial obligations to the alliance, warning that a failure to do so could result in America shifting its level of commitment to the organization.

“I owe it to you all to give you clarity on the political reality in the United States, and to state the fair demand from my country’s people in concrete terms,” Mattis said.

“America will meet its responsibilities, but if your nations do not want to see America moderate its commitment to the alliance, each of your capitals needs to show its support for our common defense.”

NATO is composed of twenty-eight member nations, each of which is obligated by its charter to devote two percent of their gross domestic product to defense spending.  However, only five of the twenty-eight have been meeting those requirements, with the United States footing the overwhelming majority of the bill.  Presidents Obama and Trump have both made critical statements regarding NATO members failing to meet this obligation in the past, but concerns were heightened when Trump suggested that the United States’ commitment to NATO may waiver under his administration if other nations don’t start taking their parts of the deal more seriously.

“No longer can the American taxpayer carry a disproportionate share of the defense of western values,” Mattis said. “Americans cannot care more for your children’s security than you do. Disregard for military readiness demonstrates a lack of respect for ourselves, for the alliance, and for the freedoms we inherited, which are now clearly threatened.”

One would think that NATO member-states would have plenty of motivation to reach their spending goals, as concerns about Russian aggression have plagued the organization since Russia’s military annexation of Crimea in 2014.

The United States has demonstrated a continued commitment to the alliance as recently as last month, when thousands more American troops arrived in various NATO nations bordering Russia to bolster defenses as a part of the NATO operation Atlantic Resolve.  American Marines were also recently deployed to Norway on six month rotations for joint training operations.  While these operations are officially not related to Europe’s concerns about Russia, it’s clear that an expanded American presence in the region is the result of Crimea’s annexation.

The only five nations currently living up to their end of the NATO bargain are the United States, Greece, the United Kingdom, Estonia and Poland.  No other nation within the organization has reached the two percent mark, despite some enjoying strong economies that could easily support it.  Countries like France, Turkey, Germany, Italy and Canada have all failed to reach the two percent mark mandated by the treaty.