United Nations climate chief Simon Stiell said the emirates' decision to appoint Sultan Al Jaber, chief executive of the Abu Dhabi National Oil Company (ADNOC), was "solely in their hands".
In an interview on the sidelines of the World Economic Forum in Davos, Switzerland, where climate change is a major topic, Stiell said Al Jaber had expressed "an openness to make this a transformative COP."
The UAE's decision to name the head of the national oil company as president of the COP28 talks has angered activists who fear it will undermine efforts to reduce greenhouse gas emissions.
"Time will tell as the weeks and months run down to COP28 as to what transformation means. A transformation has to be across the board," including "how do we close the emissions gap", said Stiell, who met Al Jaber at an energy forum in Abu Dhabi last week.
The fact that the talks are being hosted in the UAE is a decision made at COP meetings by member nations and "has to be respected, but I think it gives us an opportunity to also ask some of the hard questions," he said.
COP27, held in Egypt in November, concluded with a landmark agreement to create a "loss and damage" fund to cover the costs of the destruction that developing countries face from climate-linked natural disasters.
But an Indian-led effort to include a commitment to phase down fossil fuels was blocked at the talks, where the UAE had one of the largest contingents of oil and gas lobbyists.
"I believe they have every intention to continue their push for that, and that will be supported by other parties," said Stiell, who met an Indian delegation in Davos.
"Some of those hard questions... need to be asked and will be asked in the UAE," said the former environment minister from Grenada.
Stiell, who was appointed executive secretary of the United Nations Framework Convention on Climate Change last year, said Davos was a chance to have "frank discussions" with business leaders on their net-zero emissions pledges.
UN experts published recommendations at COP27 saying firms could not claim to be net-zero if they invested in new fossil fuels, caused deforestation or offset emissions with carbon credits instead of reducing them.
- Gore slams 'petrostates' -
Former US vice president Al Gore, a Nobel peace laureate for his work on climate change, called at Davos for COP decisions to be made by a "supermajority" instead of unanimously.
"We cannot let the oil companies and gas companies and petrostates tell us what is permissible. In the last COP, we were not allowed to even discuss scaling down oil and gas," Gore said on Wednesday.
Stiell told AFP that changing the consensus-based process was up to member countries, but that his secretariat would look at how to bring greater transparency and efficiency to decision-making.
"It's incumbent on all of us to find ways in which we can accelerate how we make decisions, the quality of those decisions," he said.
Al Jaber said Saturday that the focus should be on "holding back emissions", stressing that "as long as the world still uses hydrocarbons, we must ensure they are the least carbon-intensive possible."
- 'Back burner' -
Speakers in Davos, including UN chief Antonio Guterres, warned global political and business leaders that the world was not on track to limit warming by 1.5 degrees Celsius and would bear the devastating consequences of climate change.
"The climate crisis is one that cannot be postponed, cannot be ignored, cannot be put on the back burner," Stiell told AFP.
Swedish climate activist Greta Thunberg, taking part in a debate on the sidelines of the World Economic Forum, accused Davos elites of "fueling the destruction of the planet".
She said it was "absurd" to listen to business and political leaders attending the summit.
"It's not just about pledges, and claiming to be on a net-zero path," Stiell said.
"There is a requirement to demonstrate that those transition plans exist, those transition plans are credible and are as expansive both upstream and downstream in their value chains as possible."