"We are only at the starting line," Moon told political party leaders after his envoys revealed Kim Jong Un's offer following their return from a historic trip to Pyongyang.
He denied allegations of a behind-the-scenes agreement with Pyongyang in return for it coming to the negotiating table.
"There has been no backroom deal whatsoever with the North," Moon was quoted as saying by a spokesman of the minor opposition Bareunmirae Party.
"There will be no such a thing as a gift to the North," Moon added.
The South's leader stressed the importance of maintaining close co-operation with the US, its security guarantor, adding: "I think denuclearization talks will become feasible only when South Korea and the US take common positions" on the issue.
There would be no let-up in sanctions or pressure purely as a result of inter-Korean dialogue, he said.
"Inter-Korean talks won't be enough to achieve peace."