OSLO - The United States reaffirmed support for a UN goal of limiting global warming after criticism from the European Union and small island states that Washington seemed to be backing away.

"The US continues to support this goal. We have not changed our policy," US climate envoy Todd Stern said in a statement on Wednesday.

Almost 200 nations, including the United States, have agreed to limit rising temperatures to below 2 degrees Celsius (3.6 F) above pre-industrial times to avoid dangerous changes such as floods, droughts and rising sea levels.

The EU Commission, small island states and environmental activists urged the world to stick to the target on Tuesday, fearing that Washington was withdrawing support. Temperatures have already risen by about 0.8 degree C.

In a speech on August 2, Stern called for a more flexible approach to a new UN agreement, meant to be adopted in 2015 after past failures, so that it could be modified over time to take account of new technologies.

"This kind of flexible, evolving legal agreement cannot guarantee that we meet a 2 degree goal, but insisting on a structure that would guarantee such a goal will only lead to deadlock," he said in the speech.

In a clarification, Stern said that "my view is that a more flexible approach will give us a better chance to actually conclude an effective new agreement and meet the goal we all share".

Insistence on a more dogmatic approach in UN negotiations, that would divide up carbon rights to pollute the atmosphere, "will only lead to stalemate," he said.

Many scientists say the 2 degrees target is getting out of reach because of rising emissions, mainly from burning fossil fuels.

Emissions of carbon dioxide, the main greenhouse gas, rose 3.1 percent in 2011 to a record high. The decade ending in 2010 was the warmest since records began in the mid-19th century, UN data show.