LONDON (Reuters) - The world's leading climate coalition for the banking sector is canvassing members over changes to its rules, its chair told Reuters, following the withdrawal of some of the biggest banks and as the real economy falls short of more ambitious climate action.

Shargiil Bashir, Chief Sustainability Officer and Executive Vice President at First Abu Dhabi Bank said the move, flagged to members late on Tuesday, also reflected developments in science, policy, methodologies and regulation.

He declined to give detail on the proposals themselves, but a source with direct knowledge, speaking on condition of anonymity, said they included dropping a need to align lending with a goal of capping global warming at 1.5 degrees Celsius (3.6 degrees Fahrenheit) above the pre-industrial average.

A review into the Net Zero Banking Alliance's (NZBA) membership rules has been underway for more than a year, but pressure has mounted on the organisation since climate-sceptic Donald Trump won a second term as U.S. president.

Ahead of the inauguration of Trump, all of the six biggest U.S. banks left the banking alliance, and they were subsequently joined by Australian, Canadian, and Japanese lenders.

U.S. investment bank Morgan Stanley in October became the first of the major banks to lower its expectations for the impact it aimed to achieve from cutting loan-book emissions.

"NZBA is evolving its offer in response to changing external circumstances and member needs," Bashir said.

"Since NZBA was founded four years ago, the external landscape has rapidly changed in ways that influence the banking industry's ability to support clients to advance the net-zero transition."

(Editing by Barbara Lewis)