With less than five months to go until the COP26 climate change conference in Glasgow, the United Nations' head of climate change has warned that heads of government remain "far away" from securing a deal to limit the full consequences of global warming.

In an interview with British newspaper the Observer, Patricia Espinosa said previous promises to make one hundred billion dollars available each year to developing countries, for investment in green technology, had not been kept.

"I'd have really hoped for a clearer signal on how and when we will be able to see the commitment to mobilize the $100 billion fulfilled," she said, when asked about the prospects for a breakthrough before the conference starts on Nov 1.

"There isn't much time. We are already in the second half of June," she continued. "This is one condition to be able to have a good basis to have a successful COP26. It is essential. We cannot afford a lack of success. COP26 should be able to give some sense of hope to the world."

At the 2015 Paris climate conference, 196 countries signed an agreement pledging to reduce fossil fuel emissions, in an effort to limit temperature rises preferably to 1.5 percent, compared to preindustrial levels.

The gathering in Glasgow will be the first chance to assess what difference this has made, but after three weeks of discussion at the UN Climate Change intersessional meetings earlier this month, there was clear disappointment and frustration about what assistance has been made available to developing countries.

"The issue of climate finance still remains the most difficult part of all these negotiations," Molwyn Joseph, environment minister for Antigua, told the Financial Times. "I do not believe that particular aspect was dealt with as it should have been."

The United Kingdom currently holds the presidency of the G7 and former UN climate envoy Rachel Kyte told the Observer that the country needed to show leadership and pull countries together before COP26, to ensure a positive outcome.

"The UK has six months left to its G7 presidency and five months to go until COP26. (Prime Minister Boris) Johnson has to muster the world to significant climate finance commitments, purposing development finance and detail behind the global Marshall plan that (United States) President (Joe) Biden calls Build Back Better World. Then, and only then, can we get the agreement we need in Glasgow," she said.

COP26 was supposed to have happened last year but was postponed because of the novel coronavirus pandemic. The current intention is for it to be a physical meeting, but there are contingency plans in place.