Ashhar Alam/New Delhi

US President Donald Trump has once again stirred debate within the transatlantic alliance by floating the idea of invoking NATO’s collective defence clause, Article 5, to secure America’s southern border against illegal immigration.

In a post on his Truth Social platform on Friday, Trump suggested that calling on NATO allies to assist at the US-Mexico border could ease pressure on American security forces and allow Border Patrol agents to be reassigned to other responsibilities.

“Maybe we should have put NATO to the test,” Trump wrote, proposing that allies be compelled to help protect the southern border from what he described as further “invasions” by illegal immigrants.

The remarks come days after Trump, speaking at the World Economic Forum (WEF) in Davos, openly questioned whether NATO would stand by the United States in a moment of need. While reiterating Washington’s long-standing commitment to defend its allies, he expressed uncertainty over whether the alliance would reciprocate.

“The problem with NATO is that we’ll be there for them 100 per cent,” Trump said. “But I’m not sure they’ll be there for us.”

NATO, founded in 1949, is a political and military alliance of 32 member states. Its cornerstone is Article 5, which obligates members to come to the defence of any ally under attack. The clause has been invoked only once by the United States following the September 11, 2001 terror attacks.

Despite that precedent, Trump said he remains unconvinced of allied resolve, citing the financial and human costs borne by Washington in global security efforts.

Trump’s comments on NATO coincided with renewed attention on Greenland, where he reiterated at Davos that he would not use force to acquire the Arctic island, even as he continued to push for greater US influence over the territory a stance that has drawn concern from European partners.

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Meanwhile, immigration enforcement has emerged as a defining priority of the Trump administration’s second term. The White House has launched a sweeping crackdown on illegal immigration, tightening border controls and significantly expanding the ranks of Immigration and Customs Enforcement, with personnel numbers reportedly rising from 10,000 to over 22,000.

As Trump presses ahead with a tougher border agenda, his remarks have added a new layer of tension to US relations with NATO allies, raising questions about the future direction of the decades-old alliance.