The UN's climate chief today urged G20 nations to push COP29 negotiations toward a deal to raise money for developing nations, warning there was a "long way to go".

Negotiators worked through the night to narrow their differences at the UN talks in Baku before ministers arrive next week for the final days of the summit, but major differences remain.

UN climate chief Simon Stiell appealed for leaders of the Group of 20 nations, which includes the world's biggest economies and top polluters, to weigh in when they meet in Brazil on Monday.

"As G20 Leaders head to Rio de Janeiro, the world is watching and expecting strong signals that climate action is core business for the world's biggest economies," Stiell said in a statement.

Some developing countries, which are least responsible for global greenhouse gas emissions, want an annual commitment of US$1.3 trillion to help them adapt to climate impact and transition to clean energy.

The figure is over 10 times what donors including the United States, the European Union and Japan currently pay.

But the negotiations are stuck over a final figure, the type of financing and who should pay, with developed countries wanting China and wealthy Gulf states to join the list of donors.

The latest draft deal was 25 pages long, and still contained a raft of options.

"Here in Baku, negotiators are working around the clock on a new climate finance goal," Stiell said.

"There is a long way to go, but everyone is very aware of the stakes, at the halfway point in the COP," he said.

"Climate finance progress outside of our process is equally crucial, and the G20's role is mission-critical."