Marmol has been wrestling with the decision. The Dominican team does have right-hander Tony Pena as an option for a closer, but apparently Felipe Alou and Stan Javier, who are both on the team's coaching staff, convinced the right-hander to join them.
"They said, 'Do you want to go?' and I said, 'Maybe. Let me think about it,'" Marmol said.
He is competing with Kevin Gregg for the Cubs' closer job, and was a little nervous about leaving camp.
"I said, 'Look, it's always an honor to represent your country,'" Cubs manager Lou Piniella said. "We're not here to make decisions for you. If you feel you want to go, it's the right thing to do. Like I told everybody else, be careful, and I wished him well.
"He's told me three different times he's going, and three different times he's not going. I'm more confused than he is."
Piniella also told Marmol not to worry about the Cubs' job.
"I told him it's not going to make any difference closing-wise," Piniella said. "I said, 'We're going to still let you all compete when you get back,' and that's the end of it. I hope he pitches well and he's happy with that, and so am I."
Marmol, who was Kerry Wood's setup man last year with the Cubs, will throw on the side Saturday and pitch for the Cubs on Monday against Arizona before leaving Tuesday to join the Dominican team.
"I think someday I'll close," Marmol said. "Maybe this year."
Carrie Muskat is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.