Belgium has sworn in a new government after a record 541-day crisis, but the new Socialist-led coalition will face an uphill struggle to tackle problems at the root of the deadlock.

After 18 months without a government, King Albert II swore in Prime Minister Elio Di Rupo and then his 12 cabinet ministers and six secretaries of state, one by one.

"I swear fidelity to the king, obedience to the constitution and to the laws of the Belgian people," Mr Di Rupo said in French, and then in Dutch and German, the country's three languages, with his right hand raised.

Albert II, who helped steer feuding politicians across Belgium's French-Dutch language divide back to the negotiating table, shook hands with each of the members of the new cabinet.

The ceremony held at the royal palace and televised live ends one of Belgium's bleakest moments - a marathon of political haggling that last summer drew even the sovereign out of his royal reserve.

As divisions sharpen between thriving Dutch northerners and the struggling French-speaking south, the country that plays host to global institutions, such as the EU and NATO, is struggling to remain united around a joint political and economic vision.

The 6.5m people of Flanders renege on taxes destined to the 4.5m of southern Wallonia.

Notably absent from the six-party coalition built by Mr Di Rupo, who will be the first openly gay premier of the country, is the biggest party in Flanders, the powerful separatist N-VA, which pulled out of the lengthy coalition talks.

Yet Mr Di Rupo will be Belgium's first French-speaking premier in more than three decades and the first Socialist at its helm since 1974.

He will also be one of only three - with Austria and Denmark - centre-left leaders attending this week's crucial EU summit.

"The new team, especially its leader, comes carrying a huge burden," said an editorialist in Flemish daily Gazet van Antwerpen.

"Belgians want to believe in fairy tales," quipped French daily Le Monde.

It took soaring borrowing costs and a Standard & Poor's downgrade from AA+ to AA late last month to jolt Belgian's feuding politicians to set aside their quarrels and clinch a deal between six parties which together wield a parliamentary majority.

Top of the agenda for Mr Di Rupo when he outlines the new government's policy to parliament tomorrow will be €11.3bn in budget cuts, the toughest austerity measures in 70 years.

With its debt at 96% of GDP last year, just behind Greece and Italy in the eurozone, the coalition has pledged to balance the books by 2015 but many economists say it may not achieve the 0.8% growth the budget foresees.