The first tactic attempted by Moroni is to request a fair fight in the open. It is no surprise that the opposing leader Jacob, refuses. Even where he confident of victory, there was no reason to attempt it. Jacob knew that he was in an excellent position, and that he was a very real danger to the Nephites. He had no incentive to accept.
The idea that he might have accepted, however, is interesting. Moroni does not send the emissary to the king with no hope, but rather with some expectation that there might be an acceptance of the proposal. This sending of a representative to the city to be attacked was a traditional part of warfare as it developed in Mesoamerica, and the Aztecs typically sent ambassadors to cities requesting their peaceful acquiescence to the Aztec power, under threat of military action (Ross Hassig, Aztec Warfare. University of Oklahoma Press, 1988, p. 50).