Everyone read between the lines here. Don't ask me where my info comes from. But consider the following.
1) Duterte has aligned himself with China. He is getting free weapons from them.
2) Duterte has been attacking and have been critical of US politicians and US personalities. Despite the fact that he has some presence of US troops on his soil. It is because of this that he is closer friends with China.
3) His army obviously cannot oust the terrrorist from Marawi, despite their best efforts. Months already and they can't do it. Maybe too much jungle training not enough FIBUA. Maybe incompetence.
4) The best army trained for FIBUA in the world and with any level of success is the US Army.
5) Duterte cannot be seen to openly ask for US help to train his army, and even worse to place US advisors into Marawi with his soldiers.
6) So an agreement is reached between him and the US. The US will ask the PAP to offer our urban training facility to Pinoy soldiers for training. But being trained by SAF is like blind leading blind. So, the US will send instructors and advisors to train these Pinoys in Singapore's facility. In fact, many US military personnel are already in Singapore. Away from prying eyes in the Phillippines, the Pinoys can be trained by US advisors and instructors in Singapore, and then send back to fight in Marawi.