Mr De Gucht put a lot of work into negotiating the deal as he was involved in the talks until the end of 2014. During the campaign Mr Trump repeatedly attacked free trade deals between America and other countries.
Karel De Gucht: "Trump won the elections with an outspoken protectionist programme. He isn't the guy who will invest time in negotiating TTIP or the Trans Pacific Partnership. This will result in a high political cost. It means that they are leaving Asia to its own devices."
Mr De Gucht noted that a breakdown in talks will trigger political ramifications. Commission president Juncker has already called for Mr Trump to provide clarity on the economic course he now plans to take.
TTIP stands for Transatlantic Trade and Investment Partnership. Like the CETA free trade deal with Canada TTIP is supposed to organise the access of the US and the EU to each other's markets and should create the world's largest free trade zone.