By Sebastien Malo

NEW YORK (Thomson Reuters Foundation) - The world's 6 largest advertising firms are putting rivalry aside to help get the word out on the United Nations' agenda to combat global ills with a major pro bono publicity campaign, U.N. Secretary-General Ban Ki-moon announced on Friday.

In a move Ban said was the first of its kind, communication companies Dentsu, Havas, IPG, Omnicom, Publicis Groupe and WPP will pool their talent and media savvy to promote the U.N.'s Sustainable Development Goals (SDGs) in an initiative called "Common Ground".

The 17 SDGs, which make up a blueprint for tackling issues from inequality and education to conflict and climate change over the next 15 years, were adopted by U.N. member nations last year.

But getting the message across has been challenging.

Only 6 percent of European Union's population said they knew what the Millennium Development Goals - the SDG's predecessors - were in a 2013 survey by the European Commission.

When the SDGs were adopted "some of the reactions around the world were that there were too many and they were hard to communicate," Jan Eliasson, U.N. Deputy Secretary-General told the Thomson Reuters Foundation in a phone interview.

"The fact that (the advertising companies) use their enormous skills at selling products in different ways and choose to sell simply the elements of a better future for the world is thus a great gift."

The global ad blitz will start this weekend with ads pitching the SDGs running in about a dozen leading print publications including The Guardian, Le Figaro and The Wall Street Journal.

"Even fierce competitors can set aside their differences in order to serve a wider common interest," the heads of the six advertising companies said in a joint statement.

The advertising space for the print ads has been donated by the publications, WPP said in a statement, and the campaign is being carried out at no cost.

The first series of ads that will run this weekend feature portraits of people in their everyday life superimposed with text declaring that agreement over the SDGs' humanitarian objectives trumps rivalries.

Implementing the goals is estimated to cost $3 trillion each year.

(Reporting by Sebastien Malo, Editing by Ros Russell; Please credit the Thomson Reuters Foundation, the charitable arm of Thomson Reuters, that covers humanitarian news, women's rights, trafficking, property rights and climate change. Visit http://news.trust.org)