Belgians are striking because their government has made it harder for them to retire early and cut back on unemployment benefits as part of an austerity budget aimed at bringing its deficit within the EU limit of 3 percent this year.

European Union leaders are due to meet in Brussels on January 30 to discuss budget rules for governments and ways to stimulate growth in the crisis-hit continent.

As part of the strike, planes will also likely to be grounded at Belgium's main airport, Brussels Airport, after pilots agreed to take part in the stoppages, trade unions said.

"I can't say that no planes will go through, but in any case if the pilots strike then there will be little movement in the air," said Erwin De Deyn, chairman of BBTK, a leading union of private-sector workers.

A spokesman for the airport said it remained to be seen whether the pilots would in fact strike, and said he hoped to provide further details on Thursday.

Belgium's low cost airport Charleroi, used by cut-price carrier Ryanair (RYA.I), will be closed, a spokesman said, after Belgian unions said they would blockade the main entrance road to the terminal.

"There is only one access route to the airport," said Daniel Piron, general sectary of the Charleroi division of FGTB, an umbrella organisation of unions. "This access route will be blocked."

The Eurostar service linking London and Brussels will run a bus service from the French city of Lille to Brussels if the strike goes ahead, Eurostar said on its website.

The Thalys high-speed service, which links Paris, Brussels, Amsterdam and Cologne, also will not run any trains in Belgium from 2200 CET (2100 GMT) on Sunday to 2300 CET (2200) on Monday, a spokeswoman said.

Some 50,000 protesters took to the streets of Brussels in December last year to protest about the cuts, and at the end of that month workers in public transport, schools, hospitals and government offices also went on strike.

(Reporting By Ben Deighton, editing by Sebastian Moffett and Maria Golovnina)

• A Permanent Economic Emergency