Six European oil and gas companies have called for a global price on carbon as a way to curb climate-warming emissions from the burning of fossil fuels.

The chief executives of Royal Dutch Shell, BP, Eni, Total, Statoil and the BG Group made the appeal ahead of a new round of U.N. climate talks Monday in Bonn, Germany.

In a letter to U.N. climate chief Christiana Figueres and French Foreign Minister Laurent Fabius the companies said governments should introduce carbon pricing and eventually link up their carbon markets.

While that involves a cost for fossil-fuel companies, they said "carbon pricing policy frameworks" will help provide a roadmap for energy companies and investors.

Governments are expected to sign a global climate agreement in Paris in December.