Manila  - Thousands of protestors took to the streets in the Philippines on Monday hours before President Gloria Macapagal Arroyo was to address Congress.

Despite opposition by many Filipinos, Arroyo was expected to push for constitutional changes during her 19th and supposedly last state of the nation address (SONA).

Demonstrators gathered along a main highway leading to the Congress compound in the Manila suburban city of Quezon as thousand of security forces set up barricades.

A brief melee broke out as the rallyists faced off with police officers and soldiers along Commonwealth Avenue, which had been closed to traffic, injuring seven people.

The demonstrators carried placards denouncing Arroyo and her expected support for charter change, commonly referred to as cha-cha in the Philippines.

"Oust Gloria, Stop cha-cha!" read one banner that the rallyists hung from a nearby pedestrian overpass.

According to her aides, Arroyo would outline her accomplishments since she became president in 2001 as well as discuss her vision for the future of the Philippines.

While aides initially denied that Arroyo would express support for the efforts to amend the 1987 constitution, a summary of her speech showed that she will back the controversial moves.

"Lastly, the push for constitutional reform has to be continued," the Philippine Daily Inquirer newspaper quoted the summary as saying.

Critics have opposed constitutional amendments amid fears that the efforts only aimed to postpone the 2010 elections and allow Arroyo to extend her term beyond June.

Arroyo also allegedly plans to run for a seat in Congress to allow her to become prime minister once the form of government is changed to parliamentary from the current presidential system.