* US, EU support limiting warming to 2 degrees Celsius
* EU leaders next week are not expected to agree on 2030 goals
* US, China also seen working more closely together
BRUSSELS, March 13 (Reuters) - U.S. President Barack Obama and EU leaders meeting in Brussels this month will throw their combined weight behind tackling climate change, a document seen by Reuters says, in a show of developed world solidarity on the need for a new global deal.
But the guarded, diplomatic language is likely to disappoint environmentalists calling for urgent, ambitious pledges to cut greenhouse gas emissions.
"Sustainable economic growth will only be possible if we tackle climate change," a draft communique ahead of the EU-US summit on March 26 says. The text is subject to further negotiation between the European Union and the United States.
Both the European Union and the United States are preparing new pledges on cutting emissions for the first quarter of 2015, ahead of a U.N. summit in Paris that is meant to agree a new worldwide deal.
Its aim must be to limit any global average temperature increase to less than 2 degrees Celsius compared with pre-industrial levels "and should therefore include ambitious mitigation contributions, notably from the world's major economies and other significant emitters," the document said.
The European Union has sought to lead efforts to curb global warming with more ambitious carbon-cutting goals than any other bloc, but some of its member states, notably Poland, say there is no point in Europe taking the lead when it is responsible for only just over 10 percent of global emissions.
The United States, the world's second biggest emitter, together with China, the top emitter, account for about 40 percent of greenhouse gas emissions.
Earlier this month, the U.N.'s climate chief, Christiana Figueres, said closer cooperation between China and the United States could boost prospects for a U.N. deal in 2015.
European environmental campaigners say such a partnership could also marginalise Europe in the debate and in the race to keep up with technological advances to decarbonise energy.
To prepare its negotiating stance ahead of the 2015 U.N. talks, the Commission, the EU executive, in January outlined 2030 climate and energy policy, including a suggested 40 percent carbon cutting target. That compares with a 2020 goal to cut emissions by 20 percent from 1990 levels, which the European Union has almost achieved already.
The United States by contrast has said it will reduce carbon by 17 percent by 2020 compared with 2005, which equates to a fall of 3.5 percent below 1990 levels.
Just before Obama's visit to Brussels, a summit of EU leaders on March 20-21, will debate 2030 climate and energy policy, but is not expected to reach a firm agreement. Poland, which relies on coal for most of its energy, would block a deal at this point.
But Britain says Europe should not only make an early commitment to a cut of at least 40 percent, it should be willing to increase the aim to 50 percent if the rest of the world signs up to a deal.
A draft document this week said only that the European Union will submit its contribution at the latest by the first quarter of 2015, raising the possibility the European Union does not need to reach a political agreement until late this year.
Climate Commissioner Connie Hedegaard said only that next week's summit should send a strong signal.
"The sooner we have an overall signal, a political signal of what kind of ambition level we are heading for, the easier it will be to elaborate on the details," she said on Thursday. (Additional reporting by Ben Garside in Bonn; Editing by Janet Lawrence)