Marmol, who was projected as the Dominican team's closer, said he wanted to talk to Felipe Alou, the Dominican manager, and would announce his decision on Saturday. The World Baseball Classic teams are scheduled to announce their rosters on Tuesday.
Marmol is vying with Kevin Gregg for the closer's job on the Cubs.
"I want to be the closer here," Marmol said Friday. "I need to work here. I'm not sure I'm going [to the World Baseball Classic]."
Cubs manager Lou Piniella said Friday he told Marmol he would get the right-hander into two Cactus League games before he left to join the Dominican team. When told that Marmol is leaning toward staying, Piniella relayed a conversation with the pitcher.
"I told him the other day that while he's over there, Gregg will be throwing the ball 98 miles an hour getting people out," Piniella said. "I was just joking."
That may have influenced Marmol's change of heart.
"I think it's an honor to represent your country," Piniella said. "If you're chosen, and they're going to use you, I don't see anything wrong with [playing in the event] at all."
If Marmol does not go, the only regulars on the Cubs' 40-man roster who will participate include pitcher Ted Lilly (U.S. team), outfielder Kosuke Fukudome (Japan) and catcher Geovany Soto (Puerto Rico).
Carrie Muskat is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.