United States Secretary of Defence James Mattis on Wednesday said Washington may “moderate” its support for the North Atlantic Treaty Organisation if its members did not start honouring their defence spending pledges. At a closed session at Nato headquarters in Brussels, Mattis said that while the US would fulfill its role in the alliance, it was up to member nations to “show support for our common defence”, The Guardian reported.

“America cannot care more for your children’s future security than you do,” Mattis said. “I owe it to you to give you clarity on the political reality in the United States, and to state the fair demand from my country’s people in concrete terms,” he added. He called on the countries to adopt spending plans for 2017 and target dates to meet their goals by. However, he did not specify how the US would change its support for Nato if the spending pledges are not honoured, Reuters reported.

Washington has been calling on the body’s member-nations to spend at least 2% of their Gross Domestic Product on defence. However, only five of Nato’s 28 members including the US spend that much – Estonia, Greece, Poland and the United Kingdom. Other countries spend far less, including Italy and Spain, which spend only 1.1% and 0.9% of their GDP on defence. The US also contributes 70% of Nato’s funding.

Following Mattis’ address, British Defence Secretary Sir Michael Fallon said the Pentagon chief was showing the body that the “impatience of the American taxpayer is a reality”. Fallon’s counterparts from other countries also appeared to support Mattis’ view, with Czech Defence Minister Martin Stropnicky saying he was “not surprised” by the remarks. “The important point is that the United States is committed to a strong NATO and that means properly financed armed forces,” Stropnicky said.

Mattis’ remarks are in line with US President Donald Trump’s view, who frequently criticised Nato member-nations for not contributing enough to the alliance. On January 15, in an interview with The Times of London, Trump had called Nato obsolete because it was “not taking care of terror”. However, Trump has expressed his support for the body following his election win, and will attend a Nato summit in May.