CARTAGENA, Colombia, Sept 26 (Reuters) - U.S. Secretary of State John Kerry met with Venezuelan President Nicolas Maduro on Monday, the first formal meeting between the two since Kerry became the top U.S. diplomat.

The two men sat down together after a ceremony in Cartagena to mark the signing of a peace agreement to end Colombia's civil war.

"My hope is we could have a serious conversation," Kerry told reporters in Cartagena a few hours before the meeting, although he declined to provide specifics about what he thought might come out of the conversation with a leader who has been a persistent critic of U.S. policy.

(Reporting by Patricia Zengerle; Editing by Eric Beech)