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AD623 input signal offset compensation

I am using an AD623 with a MC33161 voltage monitor to monitor the temperature of a part.

V_SET is around 1.1 V, V_ACT the current temperature monitor voltage being equal to V_SET when the temperature is reached.

Reference voltage for the AD623 is 2.54V from the MC33161. Gain ist set to 213 by R1.
The circuit works well, but some temperature controllers show a difference of up to 6 mV for (V_ACT - V_SET) at stable temperature which is too much for the gain,
an out of valid temperature is indicated by the MC33161 for such an 'offset'.

Hence a compensation of one of the input voltages is needed, which has to be positive or negative, in the range +- 0 to 6 mV.

There is no negative voltage available in the circuit.
A single simple voltage divider at V_SET or V_ACT may not work due the positive as well as negative offset.

Will an OpAmp be the solution to add / subtract a few mV offset or what else can be a stable solution?

Thanks for any hints!!!