No, I mean wait them out outside of battle, that way:

A. If they don't attack you quickly, they'll lose units and, as a result, are weaker.
B. If they don't attack at all, you gain the city without a fight (just takes a tad bit longer)
C. If (and when) they do attack, you'll have a slightly weakened opponent who's forced to work aggressively and, possibly, on a time limit.

It's how I've captured all my cities, really. Most often, I find that they tend to sally out when there's only 1 turn left before the city is automatically given to you.