BRUSSELS -- NATO has pledged a commitment to "fair burden-sharing," invited Macedonia to begin membership talks, and criticized Russia, as the alliance held a contentious summit marked by discord between Washington and its European allies.
U.S. President Donald Trump had struck an angry tone ahead of the July 11 summit, repeating his criticism that the alliance's 29 member nations weren't spending enough on defense budgets. And Trump made an extraordinary direct attack on German Chancellor Angela Merkel, accusing Berlin of being captive to Russia.
At the meeting's conclusion, the alliance issued a communique that tried to show a united front on a host of issues, including the question of the alliance's most important feature -- Article 5 in the alliance treaty. Trump has in the past raised doubts about the U.S. commitment to it.
"Any attack against one Ally will be regarded as an attack against us all, as set out in Article 5 of the Washington Treaty," it said.
Trump has long complained -- often with misleading justification -- that NATO allies were not meeting spending commitments, and that Washington was shouldering the burden of the alliance's expenditures.
A 2014 commitment by the alliance obligated each member state to spend 2 percent of their gross domestic product on defense. Based on current trends, NATO estimates that 15 member states will meet the benchmark by 2024.
NATO headquarters says the alliance is on track to increase its overall defense spending by 3.8 percent in 2018, and a total of eight members are expected to reach the 2 percent benchmark by the end of 2018.
The statement released by NATO leaders made explicit reference to the spending question.
"We will continue to stand together and act together, on the basis of solidarity, shared purpose, and fair burden-sharing," it said.
"We reaffirm our unwavering commitment to all aspects of the Defense Investment Pledge…and to submit credible national plans on its implementation, including the spending guidelines for 2024, planned capabilities, and contributions," it said.
NATO's secretary general, Jens Stoltenberg, credited Trump at a July 11 breakfast meeting for pushing members to increase defense spending. He noted that European countries and Canada are expected to "add an extra $266 billion to defense between now and 2024."
WATCH: NATO leaders gather for a summit on July 11-12 amid deep divisions on trade and defense spending.
Even the commitment to 2 percent came under question from Trump. Two officials -- one European, one American -- who spoke on condition of anonymity said the president had mused about pushing for a 4 percent commitment from allies.
The decision to extend a formal invitation to the former Yugoslav republic of Macedonia was widely expected, following its settlement earlier this year of a long-running name dispute with NATO member Greece.
If the talks succeed, Macedonia will become NATO's 30th member.
Macedonia's potential membership has already angered Russia, which has long opposed the eastward expansion of the alliance, seeing it as a Cold War relic and a military threat.
The NATO statement criticized Russia, while also arguing that the alliance poses no threat to Moscow. It also reaffirmed its previous position, rejecting Russia's 2014 annexation of Ukraine's Crimea Peninsula.
"We continue to respond to the deteriorated security environment by enhancing our deterrence and defense posture, including by a forward presence in the eastern part of the Alliance," it said. "We have also suspended all practical civilian and military cooperation between NATO and Russia, while remaining open to political dialogue. NATO does not seek confrontation and poses no threat to Russia."
Trump's attack on Merkel came on the summit's sidelines during a breakfast gathering with Stoltenberg.
Trump said Germany was "totally controlled by Russia" and "captive to Russia" because of its dependence on natural gas and deals with Moscow like the Nord Stream 2 gas pipeline.
The project will bring gas from Russia to Germany's northeastern Baltic coast, bypassing countries like Poland and Ukraine and doubling the amount of gas Russia can send directly to Germany.
"We're protecting Germany. We're protecting France. We're protecting everybody," Trump said, adding that "it's very unfair to our country. It's very unfair to our taxpayers."
Nord Stream Controversy
Trump has urged NATO to look into the issue of Nord Stream 2
Washington and some European Union countries oppose the project, warning that it could give Moscow greater leverage over Western Europe.
Before their meeting on July 11, Merkel rejected Trump's criticism of the gas pipeline project with Russia and said that Germany can make its "own decisions."
Stoltenberg also pushed back against Trump's criticism.
"There are different views on the Nord Stream pipeline," he said. "It's not for NATO to decide."
"This is a national decision," Stoltenberg said. "But NATO has, of course, addressed energy security because we understand that there is a relationship between energy and security matters. We have highlighted the importance of this diversification of supplies to make sure that our energy systems are resilient."
Trump and Merkel met later in the day, in a hastily arranged one-on-one meeting. Speaking after, Trump told reporters he raised the issues of Germany's defense spending and Nord Stream 2. But he also insisted that he has "very good" relations with Merkel.
For her part, Merkel said she discussed trade and migration issues with Trump -- and that she looks forward to future exchanges with the U.S. president because "we are partners."
Trump's criticism brought pushback from NATO and European leaders even before the summit.
"America does not have and will not have a better ally than Europe," European Council President Donald Tusk said on July 10, adding that the United States should "appreciate your allies -- after all, you don't have that many."
Trump's criticism also brought some pushback from Republicans in Congress, as well. The Republican leader of the Senate said before the summit that he wasn't worried that Trump might pull out of the alliance.
And on July 11, Paul Ryan the Republican leader of the House said NATO was "indispensable" and the alliance is "as important today as it ever has been."
Among responses Trump and White House officials have suggested if NATO members don't increase spending is to reduce the U.S. military presence in Europe.Some alliance members have also privately voiced concern that Trump might also pull out of major upcoming military exercises.
On July 10, U.S. Ambassador to NATO Kay Bailey Hutchinson and the U.S. Senate both sought to allay concerns among allies that the United States was backing away from NATO, or from Article 5.
The summit is also being attended by leaders of so-called NATO partner states that are not members.
The final NATO statement pledged support to the ex-Soviet states of Georgia and Moldova, both of which have Russian troops on their territory. Both nations have also expressed interest in joining NATO someday.
"We reiterate our support for the territorial integrity and sovereignty of Ukraine, Georgia, and the Republic of Moldova within their internationally recognized borders," it said.
The summit closes on July 12 with a meeting by countries involved in the NATO-led Resolute Support mission in Afghanistan.
Ahead of that meeting, British Prime Minister Theresa May announced on July 11 that Britain will nearly double the number of its forces in Afghanistan -- to about 1,100 troops who are assisting Afghan forces in the fight against Taliban and Islamic State militants.
Stoltenberg also says he expects the NATO summit will "agree to extend funding for the Afghan forces beyond 2020," to express full support for Afghan President Ashraf Ghani's "bold peace initiative," and his government's reforms.