trump mattis
U.S. President-elect Donald Trump stands with retired Marine Gen. James Mattis following their meeting at the main clubhouse at Trump National Golf Club in Bedminster, New Jersey, U.S., November 19, 2016.Reuters

United States President Donald Trump's Defence Secretary James Mattis on Wednesday threatened the North Atlantic Treaty Organisation (NATO) nations of pulling out of the alliance if other nations do not increase military spending.

US President Donald Trump has agreed to meet NATO leaders in May, White House says

Mattis, who is on his first visit to Europe after assuming the top government position, addressed a meeting at the NATO headquarters in Brussels on Wednesday and sent a stern message to other 28 countries in the world's most powerful military alliance. The alliance includes countries like Germany, France, Canada, Italy, Norway, Spain and UK.

"I owe it to you all 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. America will meet its responsibilities, but if your nations do not want to see America moderate its commitment to the alliance, each of your capitals needs to show its support for our common defense," Mattis was quoted as saying by the Washington Post.

Mattis appeared to echo Trump's earlier statements on NATO that the US will no longer be the biggest financial contributor in the alliance and other member countries should fill their financial obligations in the pact. Trump resonating his campaign pledge, while speaking at the US Central Command headquarters on February 6, had indicated that the US will take a stricter stance towards the alliance.

Trump has always been critical of the organisation, and during his presidential campaign he had pledged to push NATO members to increase their funding to the western alliance to ease the financial burden on the United States. However, both sides of the political parties in the US are apprehensive about the idea, and many European allies fear that the Russian President Vladimir Putin may take advantage. Trump had also said that America may not be too eager to defend the Baltic countries in case of Russian attack if they do not fulfil the financial obligations of the alliance.

Trump, on previous occasions, has called NATO "obsolete" stating that it was not taking care of terror.

"I said a long time ago that NATO had problems. Number one, it was obsolete, because it was designed many, many years ago. I took such heat, when I said NATO was obsolete. It's obsolete because it wasn't taking care of terror. I took a lot of heat for two days. And then they started saying Trump is right," Trump told The Times of London and Bild, Germany's biggest-selling daily. He, however, also added, "NATO is very important to me."