JAKARTA (REUTERS) - Standard & Poor's (S&P) downgraded its outlook for Indonesia's sovereign credit rating on Thursday to stable from positive, citing concerns about stalling reform momentum.

S&P kept its credit rating for Indonesia's long-term sovereign debt at BB+, one notch below investment grade, and B for short-term sovereign debt. The move came as it raised it credit rating on the neighbouring Philippines to investment grade, the second debt agency to do so in less than two months.

"S&P is the only one of the big three to have Indonesia at sub-investment grade, making today's announcement particularly interesting. In our view, this is a justifiable move," Credit Suisse economist Robert Prior-Wandesforde wrote in a research note.

"There is more evidence of structural economic improvement in the Philippines than in Indonesia in recent years. Also, the Philippines' so-called macro vulnerability indicators are generally better than those of Indonesia - the exception being on the public finances."

Indonesia's acting Finance Minister Hatta Rajasa said: "The (revision) is a signal that there are a lot of things that need to be fixed and by doing that, market confidence will stay (strong)."