By Alister Doyle
BONN, Germany (Reuters) - Russia set itself at odds with a drive by China and the United States for rapid ratification of a global agreement to slow climate change when a senior official said on Wednesday that Moscow first wanted a clear set of rules.
Negotiating a detailed rule book for the 2015 Paris Agreement for shifting the world economy from fossil fuels could take years, in the worst case, delegates said at May 16-26 U.N. talks in Bonn on implementing the pact.
Top greenhouse gas emitters China and the United States say they plan to join the Paris Agreement this year and almost all other nations say they will ratify as rapidly as possible -before the rules are in place.
But Russia, the number three greenhouse gas emitter, questioned the plan in a rare sign of disagreement about implementation.
The Agreement can still enter into force without Russia, because it requires at least 55 nations representing 55 percent of global greenhouse gases to gain legal force. Russia, the number three emitter, only accounts for 7.5 percent.
"The core issue to create the landscape conducive to joining is the development of the book of rules," Oleg Shamanov, Russia's chief climate negotiator, told Reuters.
He said it took almost five years to produce rules for the U.N.'s 1997 Kyoto Protocol, which obliged about 40 industrialized nations to cut emissions. "We are hoping that it can be much faster this time," he said.
Shamanov said Russia fully backed the Paris Agreement. It was among 175 nations to sign at a ceremony last month in New York, a record number for a first day of a U.N. pact.
Rapid entry into force would help strengthen the deal and insulate it from possible challenges - U.S. Republican presidential candidate Donald Trump said last week he would seek to renegotiate the pact if elected.
A U.N. rule book will include how countries will report and monitor promised curbs on emissions in coming years and ways to adapt to changes in the climate such as more floods, heat waves, storms and rising sea levels.
China and the United States together account for 38 percent and big emitters such as Mexico, Indonesia and Argentina have also indicated they intend to join in 2016. So far, 17 small nations have ratified, with just 0.04 percent of emissions.
The U.S. National Resources Defense Council said nations accounting for 50.5 percent of emissions have so far signaled that they plan to join this year.
Patricia Espinosa, the incoming head of the U.N. Climate Change Secretariat, told Reuters last week that it was "not impossible" that the accord could enter into force in 2016 but that "this kind of ratification takes time."
(Reporting By Alister Doyle; Editing by Richard Balmforth)