WATCH: Congress joint session on martial law in Mindanao

MANILA, Philippines – As the martial law declaration on Mindanao expires on Saturday, July 22, President Rodrigo Duterte asks both branches of Congress to extend martial law until December 31.

In his letter sent to Speaker Pantaleon Alvarez and Senate President Aquilino Pimentel III, Duterte pointed to the "newly evolving" urban warfare tactics employed by homegrown terrorists in Marawi City as the reason government troops will not be able to neutralize the rebels by Saturday, July 22.

Duterte officially sent his letter to Congress on Tuesday, July 18. 

The President declared martial law in Mindanao after the military clashed with members of the Maute Group and Abu Sayyaf Group starting on May 23. 

The 1987 Constitution allows the President to declare martial law for a maximum period of 60 days. Any extension requires the approval of both the House and the Senate, which will be holding a special session to discuss Duterte's request. – Rappler.com