Lee made the remark during an Arbor Day ceremony at the Korea National Arboretum, saying steel giant POSCO has been carrying out a forestation project in Uruguay to earn credits to offset its carbon emissions and he hopes to also see such a project in the communist neighbor.
"Rather than going to South America to substitute carbon emissions, if we plant trees in North Korea and make it lush with forests, it will be helpful not only to North Korea but would also be helpful to our companies," Lee said.
Lee has advocated the idea since he took office in early 2008 but it has never materialized due to political and security tension between the Koreas. Relations between the two have been bad throughout Lee's term as Pyongyang responded to Lee's hard-line policy on it with threats and deadly provocations.
Tension has run high in recent weeks after North Korea announced it would launch a long-range rocket to put what it claims is a satellite into orbit, a move widely seen as a pretext to disguise a banned test of its ballistic missile technology.
The North said it will launch the rocket as early as next week.