presidential candidate Mitt Romney on Thursday spurned chief rival Newt Gingrich's challenge for a one-on-one debate ahead of the Jan. 3 Iowa caucuses but dismissed the notion - suggested by the former House speaker - that he's afraid to participate in such a face-off.

"We've had many occasions to debate together and we'll have more, I presume quite a few more, before this is finished," Romney told The Associated Press. "But I'm not going to narrow this down to a two-person race while there are still a number of other candidates that are viable, important candidates in the race. I want to show respect to them."

Gingrich has called on Romney to condemn or defend attack ads airing in Iowa by groups friendly to the former Massachusetts governor. Campaigning Thursday in Virginia, Gingrich told reporters that Romney's decision "tells you a lot about Gov. Romney." Gingrich said he will continue to say that Romney "doesn't mind hiding out behind millions of dollars of negative ads, but he doesn't want to defend them. The ads are false."

Gingrich said he doesn't think Iowans will reward "falsehoods by millionaires."