  We show that ultracold chemical reactions can be manipulated and controlled
by using Rydberg-dressed interactions. Scattering in the ultracold regime is
sensitive to long-range interactions, especially when weakly bound (or
quasi-bound) states exist near the collision threshold. We investigate how, by
Rydberg-dressing a reactant, one enhances its polarizability and modifies the
long-range van der Waals collision complex, which can alter chemical reaction
rates by shifting the position of near threshold bound states. We carry out a
full quantum mechanical scattering calculation for the benchmark system
H$_2$+D, and show that resonances can be moved substantially and that rate
coefficients at cold and ultracold temperatures can be increased by several
orders of magnitude.
