By Mukesh 
The story so far:
Last week, in an interview to the British newspaper, U.S. President Donald Trump said withdrawing U.S. membership from the North Atlantic Treaty Organisation (NATO) is now “beyond reconsideration”. Through this, he indicated that one of America’s oldest alliances since World War 2 could be on the brink of a break-up.
The tough words, and the U.S. President’s description of NATO as a “paper tiger”, reflect an antagonism that goes back more than a decade that has been heightened during the ongoing war with Iran. Even so, the U.S. may not find it easy to exit the 32-nation, 76-year old alliance.
A betrayal foretold: On the U.S. and NATO alliance
Why is Mr. Trump angry with NATO?
The immediate trigger for Mr. Trump’s comments to The Telegraph was that most NATO allies refused U.S. requests for military and airspace support in connection with the war against Iran, where the U.S. has faced significant setbacks in recent weeks.
While Spain and Italy have directly criticised the U.S.-Israeli strikes on Iran, France has denied U.S. military jets overflight permission to fly to Israel. Even the U.S.’s closest allies — the U.K., Germany, and Canada — have refused to take part in operations.
U.S. officials feel that this stand violates Article 5 of the North Atlantic Treaty, which states that “an armed attack against one NATO member shall be considered an attack against them all”.
Two days before Mr. Trump’s interview appeared, U.S. Secretary of State Marco Rubio had also told an American television channel that NATO’s founding principles and membership would have to be “re-examined”. “If NATO is just about us [the U.S.] defending Europe if they’re attacked, but them denying us basing rights when we need them, then that’s not a very good arrangement,” Mr. Rubio said.
The seeds of U.S. discontent with NATO had been planted by Mr. Trump ever since his first term as President, when he announced that NATO was “obsolete”. He criticised European allies for not pulling their weight in military expenditure while depending on the U.S. for their defence. In Mr. Trump’s second term, the rift grew over his rough treatment of Ukraine. More recently, he was angered that NATO members criticised the U.S.’s regime change operations in Venezuela and that they fiercely opposed his plans to annexe Greenland. With the U.S.-Israel war with Iran entering its sixth week, and no exit strategy in sight, European allies have become more determined in not joining the operations.
What is the purpose of NATO?
NATO (or OTAN, according to the French abbreviation) was formed in 1949, with the U.S., Canada and 10 West European countries which felt threatened by the Soviet Union, particularly after the installation of pro-Soviet Communist regimes in Eastern Europe and China. The North Atlantic Treaty, signed in Washington DC on April 4, 1949, created the inter-governmental military grouping mandated with “collective security”. Over time, NATO gathered more members, including Greece and Turkey in the 1950s and Spain in 1982.
After the collapse of the Soviet Union, more than a dozen East European countries joined, triggering a backlash from Russia. After Russia’s 2022 invasion of Ukraine, which was not a member, Finland and Sweden joined NATO, taking the total membership up to 32.
Ironically, although NATO was set up to counter the Soviet threat, NATO forces did not carry out a single military operation during the Cold War; it was only after conflicts in the Baltic states in the 1990s that NATO forces began joint operational missions, such as in Iraq (1990 and 2003), Bosnia (1992), Kosovo (1999), and Afghanistan (2001).
NATO does not have a separate independent force, but when required, combines resources and personnel of the 32 members that operate under a unified command structure called the Supreme Headquarters Allied Powers Europe (SHAPE), based in Belgium. It is led by the Supreme Allied Commander Europe, a U.S. 4-star General or Admiral who heads the U.S. European Command.
Although Ukraine has now backed away from plans to join NATO, Ukrainian forces have worked closely with NATO after Russia launched its ‘Special Military Operations’ in February 2022. They have received major aid packages, including a $40 billion pledge at the NATO Summit in 2024, training, and security assistance.
As a result, Mr. Trump has complained that when it came to his demands that NATO members support U.S. operations in Iran, send their navies to help open up the Strait of Hormuz, or facilitate refuelling and overflight missions, their response should have been “automatic”.
“We’ve been there automatically, including Ukraine,” he said. “Ukraine wasn’t our problem. It was a test, and we were there for them, and we would always have been there for them. They weren’t there for us,” he told The Telegraph.
How much does the U.S. fund NATO operations?
Throughout all these operations, the U.S. has provided much of NATO’s funding, including 62% of the defence spending and about 15% of the civil budget of the alliance. It also provides NATO countries with a “nuclear umbrella” and maintains U.S. military bases that enhance deterrence in the region. Under increasing security concerns and U.S. pressure, all NATO members agreed at the 2025 Hague Summit to raise defence spending to 5% of their GDP by 2035, but Mr. Trump has continued to chide allies to share more of the burden.
How hard would it be for the U.S. to pull out of NATO?
A U.S. exit from NATO or the Alliance Treaty seems unimaginable and is many times more difficult than its exit from more than 60 different multilateral organisations and treaties, including the World Health Organization and the United Nations Framework Convention on Climate Change in January 2026, and much more legally complex than the U.K.’s exit from the European Union (Brexit) in January 2020.
Article 13 of the North Atlantic Treaty provides for the withdrawal of any member, but says the member must submit a one-year “notice of denunciation… to the Government of the United States of America, which will inform the Governments of the other Parties.” As the depository authority, the U.S. government would therefore have to hand itself the notice, and then inform other countries, which would make for an awkward process.
In addition, and as a measure against Mr. Trump’s own statements in his first tenure, the Biden administration pushed a law through the U.S. Congress in 2023 that prohibits the U.S. President from trying to “suspend, terminate, denounce, or withdraw the United States from the North Atlantic Treaty — without the advice and consent of the Senate or an act of Congress”. Alternative paths could see the U.S. withdraw personnel from SHAPE or skip NATO meetings — in the manner India has withdrawn from attending SAARC summits — which would make the organisation virtually defunct.
In terms of its impact on the world order, especially in the midst of a war, the U.S.’ withdrawal from NATO would lead to the remaking of all global security structures, severely weaken the hold of the Western coalition, and strengthen other global powers such as Russia and China. It is therefore more likely that both the U.S. and its NATO allies will work to avoid such a drastic step, beginning with the visit of NATO Secretary General Mark Rutte to Washington on April 8.
As per the Nort hAtlantic Treaty, the U.S. government would have to hand itself the exit notice, and then inform other countries, which would make for an awkward process