BONN, Germany (Reuters) - At least 15 countries have joined an international alliance to phase out coal from power generation before 2030, delegates at U.N. climate talks in Bonn said on Thursday.

Britain, Canada, Denmark, Finland, Italy, France, the Netherlands, Portugal, Belgium, Switzerland, New Zealand, Ethiopia, Mexico and the Marshall Islands have joined the Powering Past Coal Alliance, delegates said.

The alliance aims to have 50 members by the next U.N. climate summit in 2018 to be held in Poland’s Katowice, one of Europe’s most polluted cities.

But some of the world’s biggest coal users, such as China, the United States, Germany and Russia, have not signed up.

Powering Past Coal comes just days after U.S. administration officials, along with energy company representatives, led a side event at the talks to promote “fossil fuels and nuclear power in climate mitigation.”

The event triggered a peaceful protest by anti-coal demonstrators and jarred with many ministers who are working on a rule book for implementing the 2015 Paris Agreement, which aims to move the world economy off fossil fuels.

The alliance was kicked off by Britain, Canada and the Marshall Islands, who urged other nations to join them in a letter seen by Reuters on Wednesday.

A source close to the matter said signatories to the alliance so far had been at least a dozen, in addition to some U.S. states, Canadian provinces and businesses.

“It is a rebuke to (President) Donald Trump from the UK and Canada, two of America’s closest allies, that his obsession for dirty energy will not spread,” said Mohamed Adow, international climate lead at Christian Aid.

Since signing the Paris Agreement in 2015, which aims to wean the world off fossil fuels, several countries have made national plans to phase out coal from their power supply mix.

(This version of the story removes reference to Chile in paragraph two after Chilean ministry says not part of the alliance).