* Britain, Canada, Marshall Islands launched initiative
* Alliance to share technology, encourage others
* Coal must be phased out to meet Paris goals - minister (Updates throughout after official announcement)
BONN, Germany, Nov 16 (Reuters) - Twenty countries and two U.S. states have joined an international alliance to phase out coal from power generation before 2030, environment ministers said on Thursday.
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.
The Powering Past Coal alliance brings together many of these countries and others that will commit to phasing out coal, sharing technology to reduce emissions, such as carbon capture and storage, and encouraging the rest of the world to cut usage.
Coal is responsible for more than 40 per cent of global emissions of the greenhouse gas carbon dioxide.
The alliance includes Angola, Austria, Belgium, Britain, Canada, Costa Rica, Denmark, El Salvador, Fiji, Finland, France, Italy, Luxembourg, the Marshall Islands, Mexico, the Netherlands, New Zealand, Niue, Portugal and Switzerland, ministers said.
The U.S. states of Washington and Oregon, as well as five Canadian provinces have also signed up.
The alliance, which is not legally binding, aims to have at least 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.
"To meet the Paris Agreement target of staying below 2 degrees, we need to phase out coal," Canada's Environment and Climate Change Minister Catherine McKenna told a news conference to launch the alliance initiative.
"There is also an immediate urgency - coal is literally choking and killing our people. The market has moved, the world has moved. Coal is not coming back," she added.
POWERING PAST COAL
But some of the world's biggest coal users, such as China, India, the United States, Germany and Russia, have not joined.
The pace of Germany's exit from coal power has dominated talks in Berlin this week on forming a new German government.
The Powering Past Coal launch 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.
"We show that even if the United States withdraws (from the Paris Agreement), we stand united and this initiative underlines that," Danish Energy and Climate Minister Lars Christian Lilleholt said.
Graham Winkelman, who heads mining firm BHP Billiton's efforts to combat climate change, told Reuters the company supported initiatives such as Powering Past Coal but said the needs of different countries had to be taken into account.
"In relation to agreements to end the use of coal, we recognize that countries will take different paths depending on their current energy mix," he said, adding that reducing emissions was the "most important objective."
The alliance was kicked off by Britain, Canada and the Marshall Islands, which urged other nations to join them in a letter, which was seen by Reuters on Wednesday.
The Marshall Islands, a low-lying island nation vulnerable to the effects of climate change and rising sea levels, said coal was the biggest barrier to curbing rising temperatures.
"Keeping it in the ground is the safest way to keep us below the survival climate threshold set out in the Paris Agreement," said David Paul, environment minister of the Marshall Islands.
(Reporting by Nina Chestney; Editing by Edmund Blair)