It manifests itself in very subtle ways:
Barack Obama is to ask the US Congress for an extra $200m in military aid to help Israel get a short-range rocket defence system in place.
The system is designed to shoot down mortars and rockets from Gaza or Southern Lebanon with guided missiles.
The system, called Iron Dome, has gone through testing and installation will start later this year.
According to US State Department figures, direct military aid to Israel was $2.55bn in 2009.
This is set to increase to $3.15bn in 2018.