Speaking on Monday, Antoine acknowledged that numerous concessions have been made, but said this was "not enough."
So far, Belgium has been unable to sign up to the deal as the southern region of Wallonia is blocking all progress. A signing ceremony with the Canadian Prime Minister was planned in Brussels this week but now looks unlikely to go ahead.
In Belgium, the regions are responsible for international trade in their region and Wallonia was specifically concerned, said Antoine, that some agreements were not sufficiently binding and Walloon farming would be threatened by CETA. He also said the region opposes the creation of trade dispute settlement courts and the treaty still opens the way for such courts to be established.
Belgian Prime Minister Charles Michel has convened a meeting of Belgium's devolved governments on Monday in a bid to resolve the issue.
A separate intervention by European Parliament President Martin Schulz appears to have had little impact.
On Saturday, the German MEP had two separate "very constructive and fruitful meetings" in the European Parliament in Brussels with Chrystia Freeland, the federal Minister of international trade of Canada and with Paul Magnette, the Minister-President of Wallonia, on the issue of CETA.
Afterwards, Schulz said, "These meetings give me much reason for optimism about the positive conclusion of CETA as soon as possible.
"During my meeting, it was clear that the negotiations between Canada and the EU are now closed and that Canada remains absolutely keen to sign CETA at the earliest possible date."
The Socialist deputy said "the few remaining issues" which stand in the way of the adoption of CETA "are for us Europeans to solve."
He said, "My meeting with Magnette, to which the Commission's services were also associated - and for whose support I am grateful, confirmed that none of the stumbling blocks on the way of CETA's adoption by Belgium are insurmountable.
"The contrary is true: the meeting already set out the next steps needed to give further clarity and legal certainty to meet the concerns raised by the Walloon Parliament and which are shared by many citizens in Europe."
Schulz said he was "convinced" that the "apparent European division" on CETA could still result in a "victory for every participant to the agreement."
Further ECR group Chair Syed Kamall, who said, "Nobody should be pleased to see this turn of events. We all want to see a strong and prosperous Europe, and the agenda of opening trade across the Atlantic was a critical way for the EU to compete with fast-rising economies that do not always share much-vaunted European values."
He added, "The irony here is that Socialists who claim to want to help Europe's unemployed have just dealt them a body blow by maintaining artificial trade barriers for small businesses that prevent them from expanding and taking on staff. It also means that consumers will continue to pay more for goods imported from Canada.
"The free trade agenda in Europe is on life support, and countries across the planet that are looking to open trade with the EU will be wondering whether it is worth years of effort. The Walloon Parliament was given the power to reject this agreement and it is only right that their decision was respected, but it is also only right that they now understand the consequences of their decision.
"There is one positive outcome. For years, we have sought an answer to the infamous Kissinger question of who to call when you want to speak to Europe. It seems the answer is the Walloon Parliament."
Elsewhere, GUE/NGL group leader Gabi Zimmer criticised the European Commission and Council for its "secret" negotiations and "backroom deals" following the failed talks.
She said, "The Commission and Council have to accept whether they'll want to continue backroom negotiations when it comes to trade agreements or if they'll start taking on board the serious concerns and criticisms of our citizens in future."
Zimmer has now urged the Commission and Council to "rethink" their approach on trade "in order to work towards and better improve the protection of social, ecological and democratic standards."