"We have leverage over the US national debt. The European Union owns assets worth 1,500 billion dollars. That is a huge amount. The United States needs to refinance several trillion dollars a year. This is a very effective tool that we have not used so far, but we may have to use it, and we do not have to be afraid of that," Hayer said in an interview published on X.
The EU could also deprive the United States of access to its market with 450 million consumers, the official added.
"NATO will cease to exist in the event of Trump's attack on Greenland," Hayer said.
US President Donald Trump has repeatedly said that Greenland should become part of the US, citing its strategic importance for national security and the defense of the "free world," including from China and Russia. Danish and Greenlandic authorities warned the US against seizing the Arctic island, noting that they expect respect for their shared territorial integrity.
A Danish colony until 1953, Greenland is now a self-governing territory within the Kingdom of Denmark. It achieved full autonomy in 2009, securing the right to independently determine its domestic affairs.