By Natalia A. Ramos Miranda

SANTIAGO, March 18 (Reuters) - Chile's new leftist President Gabriel Boric highlighted his environmental credentials on Friday, signing the country up to the United Nation's Escazu Agreement, a U-turn from the previous government which had held back from supporting the treaty.

Chile, the world's top copper producer, initially promoted the treaty, focused on access to information and environmental justice in Latin America and the Caribbean, but later refused to sign it on grounds that it could generate legal uncertainties.

But Boric, who took office this month replacing center-right President Sebastian Pinera, has pledged to take a strong position on climate change and environmental regulation.

"This agreement represents a milestone on the way to a new relationship between the State and its inhabitants in environmental matters," Boric said.

The move still has to be signed off by Congress.

The treaty, signed in 2018 by many regional countries including Argentina, Mexico and Brazil, came into force in April last year with the aim of protecting the rights of people "to live in a healthy environment and to sustainable development."

That includes access to environmental information, potentially important in countries like Chile where questions over water use by copper and lithium firms and the impact of mining on glaciers could have important business impacts.

Some 24 countries in the region had signed the treaty and 12 have ratified it.

"We are facing the worst ecological crisis in history and we need to face it jointly. We will not be successful alone," said Minister of the Environment Maisa Rojas, who is a climatologist.

"The first and only environmental treaty in Latin America and the Caribbean emerges as a powerful tool for the change we long for." (Reporting by Natalia Ramos; Editing by Adam Jourdan and Paul Simao)