A landmark agreement between North America's Pacific Rim states and provinces will be announced later today.

The governors of Western U.S. states and a Canadian province will announce a partnership to collectively combat climate change and promote clean energy. 

Governors of California, Oregon, Washington and the premier of British Columbia on Monday will announce the partnership at an event in San Francisco.

Few specifics were available. Governor Jerry Brown's office said the states and Canada will formally align climate policies to cut greenhouse gas emissions from vehicles and industrial sources. 

The effort links together economies with a combined GDP of $2.8 trillion, the fifth largest in the world. The news conference is scheduled for 4 p.m.