The announcement came after the return to power of US President Donald Trump, who has frequently castigated European members of the alliance for not investing enough in their militaries.

The mercurial Republican leader has in the past thrown into question whether the United States would protect NATO members who did not meet the spending threshold, which he recently suggested should be raised to five percent of GDP.

At just 1.55 percent of its 2024 GDP, Portugal's investment in defence places it close to the bottom of the NATO pile.

Lisbon committed at last summer's NATO summit in Washington to reach the two-percent threshold by 2029.

And after a meeting on Monday with the alliance's chief Mark Rutte, Portugal's Prime Minister Luis Montenegro said his country was ready to go beyond that and meet the minimum earlier.

"We are ready to bring forward even further the timetable for our trajectory of investment in this area," he said.

Montenegro said that decision was made with "current geopolitical circumstances" in mind.

However, he denied that Trump's return to the White House had influenced the choice to accelerate Portugal's spending plans.

"This is not a response to the new American administration that has just taken office," Montenegro insisted.

Rutte said he welcomed the increases in the country's defence spending.

"But we also know that the goal of two percent, now set a decade ago, will not be enough to meet the challenges of tomorrow," the former Dutch prime minister added.

Montenegro's meeting with Rutte came just ahead of the Dutchman's planned trip to Madrid to meet Spanish Prime Minister Pedro Sanchez.

Spain spent just 1.28 percent of its national output on defence in 2024.