(Corrects inactive stock symbol for Statoil in paragraph 12)

March 7 (Reuters) - The U.S. energy secretary blasted renewable fuels champions on Wednesday while the head of Royal Dutch Shell urged the energy sector to focus on world efforts to cut carbon emissions, revealing a yawning trans-Atlantic gap on climate issues.

Speaking at the CERAWeek conference by IHS Markit in Houston, Shell CEO Ben van Beurden outlined an ambitious plan to reduce the Anglo-Dutch company’s carbon footprint and expand in renewables, and called on others to follow.

“The energy landscape is changing fast. So we must change, where change is what the world needs,” van Beurden said.

He spoke after U.S. Energy Secretary Rick Perry struck a starkly different tone, blasting the 2015 Paris Climate Agreement to limit global warming. Perry said it was “immoral” to say people should live without fossil fuels.

“We are passionate about renewable energy. But the world, especially developing economies, will continue to need fossil fuels, as over a billion people on the planet live without access to electricity,” Perry said.

The United States, which under former President Barack Obama helped negotiate the Paris agreement, is now the only country that has backed out of the pact which calls for a gradual shift to renewable energy by the end of the century. President Donald Trump decided to withdraw last year.

Van Beurden, in an unusually strong-worded speech, said climate was the biggest challenge facing the energy sector.

“There may not be total unity behind the Paris Agreement any longer, but there is no other issue with the potential to disrupt our industry on such a deep and fundamental level.”

Perry extolled growing U.S. energy independence, as a boom in onshore shale drilling led to a rapid growth in oil as well as natural gas, the least polluting fossil fuel.

The rise of gas at the expense of dirtier coal helped the world’s biggest economy sharply reduce its carbon emissions over the last decade, as gas displaced much domestic coal demand.

“The lesson is clear (that) we don’t have to choose between growing our economy and caring for our environment, by embracing innovation over regulation we can benefit from both,” Perry said.

Shell and other European peers including BP, France’s Total and Norway’s Statoil are becoming increasingly active in the low-carbon energy sector and are vocal supporters of the Paris agreement. Until recently, climate has been less prominent in strategy presentations from U.S. rivals Exxon Mobil and Chevron.

Executives at the Houston conference repeatedly noted the ongoing increase in demand for fossil fuels, and downplayed the overall viability of renewable energy.

Other executives spoke of moving to carbon capture technologies and carbon taxes. Robert Dudley, president of BP, said Tuesday that “at some point in the future a price on carbon has to be part of this answer.”

The projected growth of oil demand is “definitely not in line with the Paris climate goals,” said International Energy Agency Executive Director Fatih Birol, saying the industry must start using carbon capture technologies.

Few were as emphatic as van Beurden, who outlined how Shell is moving to meet its targets to halve carbon emissions by 2050. Steps include limiting emissions from operations and boosting natural gas production to reach 75 percent of company oil and gas output.

“Over time, this net carbon footprint ambition will transform our company’s product mix,” van Beurden said.

Shell, the world’s top trader of liquefied natural gas, currently produces around 3.7 million barrels of oil equivalent per day, of which roughly half is natural gas.

In New York on Wednesday, Exxon Mobil Chief Executive Officer Darren Woods echoed Perry’s words at the company’s investor day, noting developing nations need solultions to generate more electricity as their standard of living increases along with the need for carbon reduction. (Reporting By Ron Bousso; Writing by David Gaffen and Ron Bousso; Editing by David Gregorio)