The 49-year-old Christian Democrat failed, during a rocky and short spell in office last year, to resolve the nation's over-riding problem: a power-sharing rivalry between its Walloon and Flemish communities.

"The government hopes to finalise an agreement in the spring of 2010, and for it to be put into action," he said, affirming a willingness to resolve a problem that Dutch speakers have demanded be addressed for several years.

He called on all parties to show "discretion and restraint" during yet another round of negotiations that are set to begin.

The thorniest issue, as Leterme is painfully aware having twice failed to resolve it, has been talks on the rights of the francophone minority in Flemish suburbs of Brussels, which became a focal point for the communal differences.

In order to avoid a repeat of the kind of squabbling which plagued Leterme's last spell in power, King Albert II has given another ex-PM, Jean-Luc Dehaene, the job of drawing up proposals to resolve the institutional malaise.

To ensure continuity, Leterme's government will be practically identical to Van Rompuy's.

The only major change required is to replace Leterme -- a somewhat gaffe-prone politician who once called his country "an accident of history" -- at the foreign ministry.

Public affairs minister Steven Vanackere was handed the foreign affairs portfolio.

Leterme's party won the last general election in June 2007 but he failed to form a coalition government until the following year.

He was forced out last December after it was alleged his aides had sought to influence a court ruling over the sale of Fortis bank after the financial crisis last year.

He was subsequently cleared of any wrong-doing and politically rehabilitated in July when Van Rompuy made him the kingdom's top diplomat.

"It's now his second chance. He has all the elements to prove he will be a good prime minister. I hope so for him and for Belgium," Van Rompuy said Tuesday.

Leterme is dubbed "Leterne," or lacklustre, in the Belgian media.

His return could stoke resentment in the relatively poor francophone community of Wallonia, as he is seen as more stridently Flemish than Van Rompuy in backing richer Dutch-speaking Flanders.

Walloons fear Flemish power-sharing demands could split the kingdom and Flemish politicians have dominated recent governments.

Leterme stunned Belgium by singing France's "La Marseillaise" when asked by a reporter if he knew the Belgian national anthem.

Other gaffes included saying the only thing Belgians have in common is "the king, the national football team and certain beers."

He disparaged French speakers in 2006 as lacking the "intellectual capacity" to learn Dutch and stoked controversy by saying his country has no "intrinsic value" as a state.