* Scientists say U.S. plan still not enough
* EU says it will over-achieve its targets for cuts by 2020
* Chinese no comment on reports Beijing might impose cap
(Recasts, updates with delegate, scientists' comments)
By Alister Doyle, Environment Correspondent
BONN, Germany, June 4 (Reuters) - The United States won praise at U.N. talks on climate change on Wednesday for its plan to cut carbon emissions, but a group of scientists said it too little to put the world on track to limit global warming.
The European Union, which often says it is doing more than the United States to lead a fight against global warming, told the June 4-15 meeting of 170 nations that it would over-achieve its targets for cutting greenhouse gases by 2020.
The United States outlined plans on Monday for the U.S. power sector to cut carbon dioxide emissions by 30 percent by 2030 from 2005 levels as part of regulations that will be the centrepiece of President Barack Obama's climate change strategy.
"It is a really constructive first step," Prakash Mathema of Nepal, leading a group of 48 of the world's least developed countries, said of the U.S. plan.
The Bonn talks are working on a U.N. deal to fight climate change, due to be agreed by late 2015 at a summit in Paris.
But Mathema and other delegates said that far more U.S. action was needed to cut emissions of gases, mainly from burning fossil fuels, that are blamed by a U.N. panel of experts for causing more floods, droughts and rising sea levels.
A group of scientists represented at the meeting said that all nations needed to do more to cut emissions and keep temperatures below a ceiling of 2 degrees (3.6 Fahrenheit) above pre-industrial times agreed by almost 200 nations in 2010.
They said that Obama's plan was insufficient even to meet Washington's own goals for tackling climate change by the end of this decade, of a cut in greenhouse gas emissions of 17 percent below 2005 levels.
"Every little step has to be welcomed ... but this is not enough to get on a 2C pathway," Bill Hare of Climate Analytics told a news conference of the report issued with research partners Ecofys and the Pik Potsdam Institute.
Among other signs of action, an adviser to the Chinese government suggested on Tuesday that Beijing may impose a cap on its soaring emissions in coming years, a huge step for Beijing which has said it needs to burn more energy to end poverty.
Chinese delegates in Bonn declined comment.
"With the EU, the U.S. and China there is a bit of jockeying for position," said Alden Meyer, of the Union of Concerned Scientists. "None of them wants to be perceived as the laggard, which is a good thing."
Connie Hedegaard, the EU Climate Commissioner, said in a statement that "the EU will substantially over-achieve" its targets for cutting greenhouse gas emissions by 2020.
EU cuts by 2020 would be 24.5 percent below 1990 levels, deeper than a minimum 20 percent target, and give a total over-achievement of 5.5 billion tonnes of greenhouse gases, she said in a statement based on data issued last month.
Greek delegation leader Ioannis Ziomas, whose country holds the rotating EU presidency, dismissed suggestions the EU was seeking to upstage the United States by touting EU successes. "This is not a beauty contest," he said.
The EU's emissions were 19 percent below 1990 levels in 2012 while U.S. emissions were up 4.3 percent, according to national data. China's emissions have more than tripled in the same period. Together, the three account for half of world emissions. (Editing by Tom Heneghan)