Belgium's outgoing Prime Minister, Guy Verhofstadt, has accepted a royal request to strive for a solution to the country's political deadlock.
Guy Verhofstadt will hold discreet talks with party leaders
Mr Verhofstadt, a Dutch-speaking liberal leader, described his mission as "very temporary and very limited".
The political crisis has left Belgium without a government since elections in June. The Dutch- and French-speaking parties are split over autonomy plans.
Flemish Christian Democrat leader Yves Leterme has given up coalition talks.
Mr Verhofstadt said he had "hesitated for a long time before accepting" the request from King Albert II.
The king asked him to "inform him in the very short term about the way to end the current impasse", a statement from the royal palace said.
There had been speculation that the king would ask Mr Verhofstadt to lead an emergency government.
Instead, Mr Verhofstadt has the job of bringing the political rivals back to the negotiating table and brokering a deal on institutional reforms.
"Our nation is going through one of the most serious political crises of the past decades," he said on Monday evening.
On Saturday, Mr Leterme, whose party narrowly won the election, gave up his second attempt to form a coalition, amid recriminations from French-speakers that his demands for greater devolution risked splitting the country.
Mr Leterme was nominated to form a government after his party came ahead in the poll, winning 30 seats in the 150-seat lower house of parliament, ending eight years in opposition.
His Flemish Christian Democrats said the Dutch- and French-speaking Liberals had signed up to his reform programme, but that the French-speaking Christian Democrats had declined to do so.
Correspondents say the French-speaking southern region of Wallonia fears that greater regional self-rule will deprive it of federal tax revenues and have a negative impact on social services.
Unemployment in Wallonia is more than double that of Flanders.
The Walloons make up about 40% of Belgium's 10.5m population, while the Flemings, who are based in the northern half of the country, represent the majority.
No single party bridges the linguistic and geographic gulf between Belgium's two regions.