Former EU ambassador the US, John Bruton says the EU should be worried about the ongoing threat of a trade war with the Trump administration.
"The EU has to be worried about that; it is indeed being threatened by the US administration, he told Euronews.
"They have threatened tariffs on EU exports to the US, particularly on the auto industry", he said.
His comments come days after it emerged that the US had downgraded the diplomatic status of the EU in Washington, after it had been raised to the level of 'sovereign state' in 2016 under President Obama.
But, Mr Bruton, who was EU ambassador to the US until 2009, said the decision to relegate the EU's standing among the ranks of ambassadors, will have "no practical implications" and is "purely symbolic."
"The EU has not enjoyed this particular protocol and privilege which it got a few years ago; it didn't enjoy it for many many years and was still extremely effective in all the things it took up" said the former Prime Minister of Ireland.
However, he said the move represents an example of the "ideological standpoint" of US President Donald Trump who is "against" multi-lateral organisations like the EU.
The former prime minister of Ireland said the EU must defend its interests and consider the leverage it has in any confrontation over trade with the US administration.
"We've got to defend our interests.
"We have considerable leverage as well. The US exports a lot of services, it has a surplus in services exports and it exports a lot of those services to EU countries, so the EU is not without means in defending its interests', he said.
"I think he [Trump] comes from an ideological standpoint which is against organisations like the European Union which believes that individual states should be completely sovereign and should be subject to no external rules at all, or no external courts at all.
"We reject that point of view and we must challenge that point of view; at every level; intellectually as well as politically."
European Commission President, Jean Claude Juncker is due to visit President Trump in the coming weeks.
Ambassador Bruton said Mr Juncker should be "firm" with the president.
"I'd be quite firm as I'm sure Jean Claude Juncker will be", he said.
Asked how, he said "by holding to the EU position; defending EU interests, not making unwarranted compromises, but showing a willingness to make reasonable compromises.
"Does anyone really think we could solve the climate challenge other than through multilateralism?
The only way we can solve global problems is through multi-lateral methods", he said.