Manila  - Police in the Philippine capital Manila were on alert Friday as thousands of people were expected to take to the streets for a rally against efforts to amend the constitution that would extend the term of scandal-tainted President Gloria Macapagal Arroyo.

More than 4,000 policemen have been deployed around Manila, especially in the financial district of Makati City where the demonstration was going to be held later Friday.

At the Malacanang presidential palace, additional security forces were deployed while container vans and barbed wire were used to block a main road leading to the sprawling compound in case protestors march to the area.

Superintendent Rommel Miranda, a spokesman for the Manila police command, said authorities expected less than 15,000 people would attend the rally.

"Today is payday and everyone is more likely inclined to think of their holiday shopping," he said.

But organizers are confident that up to 50,000 protestors would join the rally, which denounces moves by allies of Arroyo in Congress to push for amendments to the 1987 constitution.

Despite widespread public opposition, Arroyo has not asked her allies to stop the efforts - a move that critics said was an indication the 61-year-old leader is seriously considering extending her term in office.

An Arroyo ally has also filed a resolution in the House of Representatives seeking a postponement of the May 2010 elections.

Many Filipinos no longer want to see Arroyo extend her term beyond 2010 amid continued allegations of corruption and other anomalies in her administration. She has also been accused of massive cheating in the 2004 presidential elections. (dpa)