* UK sets world's toughest national emissions cut
* But say will water down if EU emissions rise faster
(Adds quotes, reaction, detail)
By Gerard Wynn
LONDON, May 17 (Reuters) - Britain on Tuesday committed to halve its greenhouse gas emissions by 2025 but made the binding target conditional on the European Union taking similar climate action.
"By making this commitment, we will position the UK a leading player in the global low-carbon economy, creating significant new industries and jobs," Prime Minister David Cameron said.
The country's emissions in 2010 were 25 percent below 1990 levels. Its long-term goal, under a binding law, is to cut greenhouse gases by 80 percent by 2050.
In making the target the government accepted advice from its statutory climate advisers on emissions from 2023-2027, of a so-called fouth carbon budget, after accepting similar recommendations for previous years.
"This is an outstanding example of strong willingness to act despite difficult economic times," said Connie Hedegaard, the head of climate action at the European Commission.
"With this decision, the UK seizes a huge economic and innovation opportunity that will make its economy more competitive in the future."
Britain is one of a handful of EU countries which want the bloc to sharpen its emissions cutting target to 2020, a shift many countries especially in eastern Europe oppose.
At present the EU says that it will only increase its ambition if all countries including the top two emitters the United States and China agree a new global deal to succeed the present Kyoto Protocol after 2012.
Many analysts say such a deal is out of reach, under U.N. climate talks long deadlocked over sharing the burden of emissions cuts between industrialised and emerging economies.
"We will review progress in EU climate negotiations in early 2014," said the UK government statement, adding that if the EU's industrial carbon emissions were falling slower than Britain's national trajectory then it would water down its own targets.
That dampened some green groups' enthusiasm.
"The inclusion of a get-out clause, in case Europe doesn't cut emissions fast enough, creates needless uncertainty that could dent business confidence," said Friends of the Earth.