US President Barack Obama and EU leaders meeting in Brussels this month are set to throw their combined weight behind tackling climate change, in a show of developed world solidarity on the need for a new global deal, leaked documents suggest.

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 communiqué ahead of the EU-US summit on 26 March says. The text is subject to further negotiation between the European Union and the United States.

Both blocs are preparing new pledges on cutting emissions for the first quarter of 2015, ahead of a UN summit in Paris that is meant to agree a new global 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 says.

Brussels 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 little more than 10% of global emissions.

About 40% of greenhouse gas emissions come from the US, the world's second biggest emitter, and China, which tops the pollution table.

Earlier this month, the UN's climate chief, Christiana Figueres, said closer cooperation between Beijing and Washington could boost prospects for a UN 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 talks, the EU executive, in January proposed 2030 climate and energy goals, including a 40% carbon-cutting target. That compares with a 2020 goal to cut emissions by 20% from 1990 levels, which has almost been achieved.

By contrast, the US has said it will reduce carbon by 17% by 2020 compared with 2005, a fall of just 3.5% below 1990 levels.

Shortly before Obama's visit to Brussels, a summit of EU leaders on 20-21March, will debate 2030 climate and energy policy, but is not expected to reach a firm agreement, due to the blocking Polish vote.

A draft document this week said only that the European Union would submit its contribution at the latest by the first quarter of 2015, suggesting that the EU may not need to reach a political agreement until late this year.

Speaking on 13 March, the EU’s climate commissioner, Connie Hedegaard, said: "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."