British Prime Minister Boris Johnson called on Monday for wealthy countries to meet a pledge to spend $100 billion a year to tackle climate change as he prepares to host a United Nations summit starting at the end of October.

Johnson and U.N. Secretary-General António Guterres will hold a roundtable of world leaders on Monday to get rich countries to deliver on the unmet pledge, made in 2009.

"Richer nations have reaped the benefits of untrammeled pollution for generations, often at the expense of developing countries," Johnson said in a statement.

"As those countries now try to grow their economies in a clean, green and sustainable way we have a duty to support them in doing so – with our technology, with our expertise and with the money we have promised."

A report released on Friday by the Organisation for Economic Co-operation and Development said that rich countries likely missed a goal to contribute $100 billion last year to helping developing nations deal with climate change after increasing funding by less than 2% in 2019.

A U.N. analysis of country pledges under the Paris climate agreement released last week said that under current national pledges, global emissions would be 16% higher in 2030 than they were in 2010 - far off the 45% reduction by 2030 that scientists say is needed to stave off disastrous climate change.

Without more ambitious commitments, global temperatures could hit 2.7C above pre-industrial levels by the end of the century, the U.N. said. (Reporting by Andrew MacAskill, Editing by Paul Sandle)