Republican presidential nominee Donald Trump said Wednesday that under his administration the United States would not automatically defend the Baltic states from Russia if they were invaded, setting off a new round of questions about his commitment to the North Atlantic Treaty Organization. But his comments also have prompted a basic question: What do the Baltic states provide for U.S. national security?

Lithuania, Latvia and Estonia became members of NATO along with four other countries in 2004, as the military alliance expanded to include formerly Communist countries in Central and Eastern Europe. At the time, then-Russian Defense Minister Sergei B. Ivanov criticized the move and said the Baltic states “are consumers of security, not producers” — ironically, a point the Republican nominee appeared to touch upon Wednesday.

NATO’s overall budget for 2016 is about $1.3 billion. According to statistics released by NATO, Washington pays about 22.1 percent of that, by far the most in the alliance. They are followed by Germany (14.7 percent), France (10.6) Britain (9.8) and Italy (8.4). Latvia, Lithuania and Estonia each pay less than 0.5 percent of NATO’s budget.

Defense spending by NATO countries has been a thorny issue this year not only with Trump but with President Obama. The focus has generally been on countries meeting their commitment to spend 2 percent of their budgets on defense, rather than contributing more to NATO’s overall budget.

In April, Obama called for European nations to do more to support the military campaign against the Islamic State and to each contribute their “full share — 2 percent of GDP — towards our common security.” The president added, “That is something that doesn’t always happen — and I’ll be honest: Sometimes Europe has been complacent about its own defense.”

In an interview for the Atlantic magazine published in March, Obama also criticized “free riders” who are “pushing us to act but then showing an unwillingness to put any skin in the game.”

New NATO documents show that in 2016, the United States will spend about 3.6 percent of its GDP on defense. Estonia will spend about 2.2 percent, with Latvia and Lithuania setting aside just less than 1.5 percent. Estonia spent about 2 percent in 2015, with Latvia and Lithuania about 1 percent.

The only other countries spending 2 percent in 2016 are Greece (2.4 percent), Britain (2.21) and Poland (2). France is close, spending about 1.8 percent.

As of this month, the Baltic countries combined had a few dozen troops among the 12,900 deployed to Afghanistan as part of the NATO-led training mission, Operation Resolute Support.

Each nation, along with Poland, also recently committed to hosting a battalion of troops from NATO to deter Russian aggression. The United States will send one from the Army to Poland, with Britain, Germany and Canada preparing to establish multinational battalions of a similar size in Estonia, Lithuania and Latvia, respectively.

Trump, asked in an interview by the New York Times what he would do if Russia invaded one of the Baltic states, said there are NATO nations that are not “not paying the bills.”

“You can’t forget the bills,” Trump told the Times. “They have an obligation to make payments. Many NATO nations are not making payments, are not making what they’re supposed to make. That’s a big thing. You can’t say forget that.”

The NATO treaty, first signed in 1949, holds that members agree that “an armed attack against one or more of them in Europe or North America shall be considered an attack against them all.” If an attack occurs, the treaty continues, each member will assist whoever is attacked by taking “such action as it deems necessary, including the use of armed force, to restore and maintain the security of the North Atlantic area.”

The treaty mentions nothing specific about paying bills but says that members promise they “will maintain and develop their individual and collective capacity to resist armed attack.” NATO calls for each member to provide collective funding for NATO operations and oversight, and agreed in 2006 to each spend 2 percent of their GDP on national defense.

Trump’s comments have prompted criticism from some U.S. officials. Rep. Eliot L. Engel (N.Y.), the ranking Democrat on the House Foreign Affairs Committee, said Thursday in a statement that the remarks show that “NATO may be facing one of its biggest threats”: Trump.

“The Republican standard-bearer has again made clear that he does not view America’s commitment to NATO as ironclad, suggesting that we might not abide by our Article 5 obligations if Russia invaded the Baltic countries,” Engel said, calling it music to Russian President Vladimir Putin’s ears.

Sen. Lindsey O. Graham (R.-S.C.), a member of the Senate Armed Services Committee and frequent critic of Trump’s when both were running for president, called on Trump to clarify his remarks and said they made the United States less safe. Putin, he said, is a “happy man” hearing them.

“The Republican nominee for president is essentially telling the Russians and other bad actors that the United States is not fully committed to supporting the NATO alliance,” Graham said. “NATO has been the most successful organization in modern history to provide collective defense for democracies.”