At approximately 10.47pm on Tuesday, 26 January officers attempted to stop two males seen with a machete on a moped in Eccleston Road, Pimlico.
The moped failed to stop and was later located in the area of Victoria Coach Station.
Two men were arrested on suspicion of causing grievous bodily harm and possession of an offensive weapon. They remain in custody.
One officer suffered minor injuries while attempting to stop the vehicle. He was taken to hospital as a precaution and has since been discharged.