Brazil and France have agreed a common position on fighting global warming before next month's UN climate change conference in Copenhagen.
They will pursue the goal of reducing industrialised nations' emissions to 50% below 1990 levels by 2050.
The BBC reports French President Nicolas Sarkozy and Brazilian President Luiz Inacio Lula da Silva announced the move in Paris.
It comes days after Britain said it was highly unlikely a legally binding climate treaty can be agreed this year.
The climate conference, in the Danish capital from 7 to 18 December, aims to create a successor to the 1997 Kyoto treaty limiting carbon emissions.