BRUSSELS, Belgium (AFP) - Belgium's King Albert II is to announce that he will abdicate on July 21, the country's national day, in a speech to the nation Wednesday, a Belgian government source told AFP.

The palace said "the king will address the people" in a speech to be broadcast live on radio and television at 1600 GMT, and the source said the monarch would announce his abdication for July 21 - confirming Belgian press reports.

The speech is to be followed 15 minutes later by a statement from Prime Minister Elio Di Rupo.

PM Di Rupo's office said that a "restricted cabinet meeting" had taken place earlier in the day "in the presence of the king". King Albert, who has reigned for 20 years and who turned 79 year old last month, has played a key role in the political life of the small language-divided nation.

It was King Albert who steered the country's divided politicians to a deal in late 2011 after the country spent a record-breaking 541 days without a government.

With the country heading to new potentially dangerous elections next year, there have been persistent rumours that the increasingly frail monarch might follow in the footsteps of Dutch Queen Beatrix, who abdicated in January.

King Albert's heir is his eldest son Philippe, aged 53.

The RTBF TV network said it would be the first abdication in the history of Belgium. The country gained independence from the Netherlands in 1831.

King Albert is the second son of King Leopold III (1901-1983) and Astrid of Sweden (1905-1935), and ascended to the throne in 1993 after the death of his older brother King Baudouin, who died without an heir.

Six kings from the house of Saxe-Coburg-Gotha - now known simply as the royal house of Belgium - have headed the constitutional monarchy since independence.

As monarch, King Albert's duties include representing Belgium at home and abroad on state visits, trade missions, and at high-level international meetings as well as taking an interest in Belgian society, culture and enterprise.