The debate on whether the world needs stronger greenhouse gas cuts to keep the planet from warming by 2C should be deferred until next year, according to Brazil's lead negotiator at the upcoming talks in Doha.

Ambassador Luiz Alberto Figueiredo says delegates at Qatar – the most important climate negotiations of the year – should prioritise an extension of the Kyoto protocol and the rules for a longer-term agreement rather than be distracted by the crucial but contentious issue of emissions reductions.

Environmental groups, however, are calling for greater urgency from Brazil, a country that has won plaudits at previous gatherings for leading the search for common ground between wealthy and developing nations.

With the Kyoto protocol set to expire at the end of the year, Figueiredo told the Guardian there is an urgent need to ensure the continuation of a process that has been the foundation of international discussions for more than a decade, despite its shrinking support among the initial signatories.

"We need a strong second commitment period and we need to decide duration," said Figueiredo, who says Brazil would like the new phase of Kyoto to last until 2020, when a new "internationally binding protocol" is supposed to come into effect.

That new instrument – which should be far more inclusive – will also be negotiated in Qatar, but the rules do not have to be finalised until 2015. With almost universal agreement that the world is off course to achieve the targets set at the international talks in Copenhagen in 2009, some nations and environmentalists want the upcoming talks to embrace greater emissions cuts, but the Brazilian ambassador says this would be a mistake.

"We have to be very focussed on what needs to be done in Doha and not be diverted to other important issues that probably can't be solved quickly, such as the ongoing question of ambition," he said. "I don't think Doha should concentrate on that. We'll deal with that during negotiation of the next protocol."

The second phase of Kyoto is expected to go ahead but with fewer nations compared to number that agreed to cut emissions in the original 1997 deal. The US signed but never ratified that agreement because obligations were not imposed on big developing economies like China, India and Brazil. More recently, Japan, Russia, Canada and New Zealand have indicated they will not sign up to a second commitment period.

This leaves only the EU countries, Australia and probably Norway and Switzerland that will recommit. These account for a minority and declining share of world emissions, but Brazil and other developing nations say size is unimportant as long as the principles of Kyoto – particularly the idea that earlier developed nations should shoulder a bigger burden – are maintained. Countries currently outside of a binding deal, such as the US, China and Brazil, are supposed to implement voluntary pledges made at the Copenhagen conference. But scientists say the commitments on the table are far from sufficient to stay within the 2C goal.

Environmental NGOs say greater urgency is needed at Doha. "We don't have the time to wait to talk about ambitions until next year," said Jennifer Morgan of the US-based World Resources Institute. "I hope Brazil will bring parties together both to finalise the Kyoto protocol and also to talk about ambition now.