NATO Secretary-General Jens Stoltenberg says that alliance members are to agree on May 25 on NATO's participation in the international coalition against the extremist group Islamic State (IS).
"This will send a strong political message of NATO's commitment to the fight against terrorism," Stoltenberg said ahead of a meeting of leaders of the 28-member alliance in Brussels -- the first such gathering to be attended by U.S President Donald Trump.
However, Stoltenberg stressed the plan did not provide for NATO taking on a combat role in the fight against IS and other extremist groups in Syria and Iraq.
All 28 NATO members are already individually members of the 68-nation U.S.-led Global Coalition, whose goal is to defeat IS, but NATO as an organization has not followed suit until now, despite pressure from the United States.
Member states such as France, Germany, and Italy had reportedly opposed such a move to avoid dragging the alliance into a ground war and risk harming relations with Arab powers.
Trump called NATO "obsolete" during the U.S. presidential campaign, saying it was failing to focus on the threat from Islamist terrorism and meet its defense spending commitments.
But he said in April that it was "no longer obsolete" after many allies -- following repeated exhortations by senior U.S. officials earlier this year -- started making plans to increase their military spending and incorporate counterterrorism into NATO's mission.
Diplomats from NATO nations have told RFE/RL that the alliance is expected to formally join the coalition.
Talk at the NATO meeting is expected to focus on two main topics: Getting all 28 NATO members to reach agreed defense spending targets and combating terrorism against the backdrop of the May 22 bombing in Manchester, England, that killed 22 people.
Stoltenberg said NATO would expand the role of its AWACS surveillance planes in supporting anti-IS operations and step up training programs in Iraq.
NATO will agree on an action plan to better fight terrorism in Europe, create a specialized cell at the alliance's headquarters, and appoint a coordinator of antiterrorism operations.
He said the allies would also meet Trump's demands to share more of the security burden and reaffirm a commitment to spend two percent of annual gross domestic product on defense.
U.S. Secretary of State Rex Tillerson told reporters aboard Air Force One as it flew toward Brussels on May 24 that President Donald Trump, on his first foreign trip since taking office in January, wants NATO members "to step up and fully meet their obligations" of spending 2 percent of gross domestic product on defense.
Only the United States, Britain, Poland, Estonia, and Greece met the NATO spending target last year while Latvia, Lithuania, and Romania came close to the target.
Washington funds about 70 percent of NATO spending, and all members share the costs of running the alliance's day-to-day administration and building costs.
Trump has recently softened his criticism. In April, he said NATO is "no longer obsolete" after many allies -- following repeated exhortations by senior U.S. officials earlier this year -- started making plans to increase their military spending and incorporate antiterrorism into NATO's mission.
Arriving in Brussels on May 24, Trump said the deadly bomb attack in Manchester only showed how dangerous the threat was and that the fight against terror had to be won.
The extremist group IS claimed responsibility for the May 22 attack, in which a suspected suicide bomber set off explosives as concertgoers were leaving Manchester Arena after watching American pop singer Ariana Grande perform.
The blast killed 22 people and injured about 60 others. Many of the victims were children, including an 8-year-old girl who was among the dead.
Twenty-three of the Global Coalition's partners have over 9,000 troops in Iraq and Syria in support of the effort to defeat IS, while its air assets have conducted more than 19,000 strikes on IS targets.
All 28 NATO allies have joined the coalition as individual countries, but Stoltenberg said that, if the alliance became a member, it would significantly boost coordination in the war against IS.
It would also send "a strong message of unity...and especially in light of the attack in Manchester, I think it is important to send this message of unity against terrorism," Stoltenberg said.
"Many allies would like to see NATO as a full member of the coalition," he said.
Turkish President Recep Tayyip Erdogan said on May 24 that the Manchester bombing showed terrorism was a global problem and that NATO allies should cooperate more closely and share information swiftly to confront it.
In addition to slamming NATO during the U.S. election campaign, Trump also took aim at the city that is now hosting him, calling Brussels a "hellhole," citing a lack of "assimilation" by Muslims living there.
On May 24, hundreds gathered at a Brussels trains station with banners and placards denouncing Trump as a sexist and a racist and accusing him of ignoring climate change and social issues.