Greenpeace issued an unreserved apology and shipped its director to Peru to make amends in person to the local government, after its activists allegedly damaged the Nazca Lines, during a publicity stunt.
Peruvian authorities said they will press charges against a group of 20 environmentalists who broke into a strictly prohibited area surrounding the archaeological marvel to unfurl a banner.
"Without reservation Greenpeace apologises to the people of Peru for the offence caused by our recent activity laying a message of hope at the site of the historic Nazca Lines," Greenpeace said in a statement. "We are deeply sorry for this. We fully understand that this looks bad."
Peruvian officials said the activists harmed the UN World Heritage site by lines by leaving footprints in the adjacent coastal desert.
Access to the Nazca Lines, which consist of massive depictions of animal and plants drawn on the desert's surface up to 2,000 years ago, is restricted and visitors have to put on special footwear not to leave traces behind.
Greenpeace activists accessed the site without notifying authorities to lay a message promoting clean energy beside the famed figure of a hummingbird ahead of the UN climate talks in the capital, Lima.
The message, visible like the Nazca lines from an airplane, read: "Time for a change, the future is renewable."
Deputy Culture Minister Luis Jaime Castillo said the stunt was a "slap in the face at everything Peruvians consider sacred".
The government has asked prosecutors to file charges of "attacking archaeological monuments" against the 20 activists, Castillo said.
No arrest was immediately made but the Minister said the government would seek to prevent those responsible from leaving the country. If convicted, they face up to six-years in jail.
Greenpeace said it was willing to accept the consequences of its actions and was to fully cooperate with investigating authorities.
"Rather than relay an urgent message of hope and possibility to the leaders gathering at the Lima UN climate talks, we came across as careless and crass," the group said.
"We take personal responsibility for actions, and are committed to nonviolence. Greenpeace is accountable for its activities and willing to face fair and reasonable consequences."
Greenpeace International executive director Dr Kumi Niadoo was due to arrive in Lima to personally apologise for the offence cause, the group added.