BRUSSELS:- Defense Secretary Jim Mattis issued an ultimatum Wednesday to allies in the North Atlantic Treaty Organization, warning that if they do not boost their defense spending to goals set by the alliance, the United States may alter its relationship with them.

“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.”

The statements came during a closed-doors meeting with defense ministers from other NATO countries and were provided to reporters traveling with the defense secretary to Brussels. It marks an escalation in Washington’s long-running frustration that many NATO countries do not spend at least 2 percent of their gross domestic product as they have pledged. President Trump often made that point during his upstart run for the White House, at various times calling the alliance “obsolete” while grousing that its 28 members need to pay “their fair share.”

Mattis, a retired Marine general, recalled Wednesday that when he was NATO’s supreme allied commander of transformation from November 2007 to September 2009, he watched as then-Defense Secretary Robert Gates warned NATO nations that Congress and the American people “would lose their patience for carrying a disproportionate burden” of the defense of allies.That impatience, Mattis said, is now a “governmental reality.”

“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.”

Currently, just five of NATO’s 28 countries spend at least 2 percent on defense: the United Kingdom, Estonia, Poland, Greece and the United States. Major members of the alliance that do not include France (1.78 percent), Turkey (1.56), Germany (1.19), Italy (1.11) and Canada (.99), according to NATO figures. Others have pledged to do so but not until 2024. Mattis said Washington needs the help of other nations already spending 2 percent to urge the others to do so. Those already with a plan to boost spending must accelerate it, and countries without one must establish one soon, he said.

The remarks come as NATO nations confront how to handle Russia following its 2014 annexation of Ukraine’s Crimean Peninsula and U.S. intelligence assessments that Russia hacked Democratic Party officials during the presidential campaign last year. Retired lieutenant general Michael Flynn, Trump’s national security adviser, resigned under pressure Monday night after revelations that he misled Vice President Pence about secret communications with Sergey Kislyak, the Russian ambassador to the United States, about sanctions put in place in response to the alleged hacking.

“Fellow ministers, when the Cold War ended we all had hopes,” Mattis said. “The year 2014 awakened us to a new reality: Russia used force to alter the borders of one of its sovereign neighbors, and on Turkey’s border [the Islamic State] emerged and introduced a ruthless breed of terror, intent on seizing territory and establishing a caliphate. While these events have unfolded before our eyes, some in this alliance have looked away in denial of what was happening.”

NATO Secretary General Jens Stoltenberg sought to downplay any suggestion that Mattis’s message constituted a threat, saying that the United States was simply pressing its allies to live up to their own commitments.

“This is not the U.S. telling Europe to increase defense spending,” Stoltenberg said at a news conference after the tough meeting. “This is 28 allies, heads of state, that all were sitting around the same table in 2014, and looking into each other’s eyes and agreeing that we shall increase defense spending.“I welcome all pressure, all support to make sure that happens,” Stoltenberg said.

Mattis’s ultimatum could have wide-ranging implications in Europe, but the biggest might be for Germany. If it were to meet the 2 percent bar, it would boost its defense spending to about $75 billion per year, resulting in a military larger than Britain’s. That would be a profound shift for a country that has long had a pacifist tradition that held it back from embracing a global defense presence as great as its economic might.

Mattis’s demands were echoed by British Defense Secretary Michael Fallon, who met head-to-head with the U.S. defense chief before the main NATO conclave. Fallon said that Britain which spends the second-largest amount on defense in the alliance is proposing that countries that spend less than NATO guidelines commit to an annual defense budget increase.

“An annual increase would at least demonstrate good faith,” Fallon told a small group of reporters in Brussels. Fallon said that Mattis had underlined a “100 percent commitment” to NATO. Britain has generally tried to ally itself with the Trump administration as London negotiates an exit from the European Union. But British leaders have urged Trump to maintain his military commitment to NATO and to Europe.