Denmark acknowledged on Thursday it had long neglected the defense of Greenland, a vast and strategically important Arctic island, after U.S. President-elect Donald Trump said acquiring the Danish sovereign territory was vital for U.S. security.

Trump, who takes office on Jan. 20, said this week that U.S. control of Greenland was an "absolute necessity" and did not rule out using military or economic action such as tariffs against Denmark to make it happen.

"We have neglected for many years to make the necessary investments in ships and in aircraft that will help monitor our kingdom, and that is what we are now trying to do something about," Defense Minister Troels Lund Poulsen told journalists.