BRUSSELS (Reuters) - The French-speaking region of Wallonia will not yield to an ultimatum set by the European Union for it to decide on a planned EU-Canada free trade deal, the president of the Walloon parliament said on Monday.

All 28 EU governments support the Comprehensive Economic Trade Agreement (CETA), including Belgium, but the latter can only sign up to it if it has the consent of five sub-federal authorities and Wallonia has steadfastly resisted.

The European Union has given Belgium until late on Monday to overcome that opposition or an EU-Canada summit on Thursday to sign the pact with Canadian Prime Minister Justin Trudeau will be canceled.

Andre Antoine, Walloon parliament president and a member of Paul Magnette's Socialist party, said it was not possible for the region to give its assent on Monday.

"There's a huge mish-mash of texts. This is not serious international law... Secondly, ultimatums and threats are not part of democracy. We want a deal, we want a treaty, but we want to negotiate it with a minimum of courtesy and respect," he said.

"A reasonable delay would be the end of the year. With that, we could get there," he continued, adding there would still be flights between Brussels and Canada in the future.

Belgian Prime Minister has called a meeting of its federal and sub-federal governments, including that of Wallonia, at 1300 CET (1100 GMT) to seek a way out of the crisis.

CETA supporters say it would increase trade between the partners by 20 percent and boost the EU economy by 12 billion euros ($13 billion) a year and Canada's by C$12 billion ($9 billion).

Walloons have concerns about the threat of surging pork and beef imports from Canada and an independent court system to settle disputes between states and foreign investors, which critics say allows multinationals to dictate public policy.

Many EU leaders suspect the local government in Namur is using its devolved powers to play domestic politics.

Dutch language Flemish newspaper De Morgen said on Monday that the Magnette's stance was both a matter of principle and opportunism, a chance to boost his reputation and to become leader of the center-left in Belgium.

The issue goes beyond just a trade deal with Canada, the EU's 12th-largest trading partner.

If CETA fails, the EU's hopes of completing similar deals with the United States or Japan would be in tatters, undermining a bloc already battered by Britain's vote to leave it and disputes over Europe's migration crisis.

(Reporting By Philip Blenkinsop; editing by Robert-Jan Bartunek)