Rich countries must do more to help developing nations cut carbon emissions, Boris Johnson will tell other world leaders at a high-level gathering in New York.
The prime minister will be hosting the meeting on climate change with UN Secretary General Antonio Guterres.
It is understood the PM is likely to focus on coal, cash support, cars and trees, which soak up carbon dioxide.
Mr Johnson is also expected to discuss global warming with President Joe Biden in a meeting at the White House in Washington.
Ahead of the gathering in New York, the PM said richer nations have “reaped the benefits of untrammelled pollution for generations”.
This has often been “at the expense of developing countries”, he added.
“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,” the prime minister said.
The UN meeting is seen as a way of galvanising action on climate change ahead of the COP26 summit, being held in the UK in November.
Earlier, however, COP26 President Alok Sharma admitted Chinese president Xi Jinping is yet to commit to attending the gathering in Glasgow, now fewer than 50 days away.
That is despite China being “key” to the talks because it is the “biggest emitter in the world”, Mr Sharma told Sky News.
He wants the Chinese to “come forward and make (COP26) a success together with the rest of the world”.
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Developed countries agreed to give $100bn (£73bn) a year to developing ones by 2020, to help them cut their emissions, Downing Street said.
But by 2019 the level had reached only $79.6bn (£58bn), more than $20bn short of the target set for the following year.
The UK has asked Germany and Canada to take a lead on developing a “$100bn Delivery Plan”, to be published ahead of COP26.
Downing Street said that at the end of the UN General Assembly this week, the UK will publish the detail of countries’ climate finance commitments to date.
The UK has already committed £11.6bn in international climate finance over the next five years, Number 10 said – twice the previous five-year commitment.
Boris Johnson will say in New York that £550m of that will be allocated to support developing countries in adopting policies and technologies that end the use of coal.
The prime minister will also be meeting Amazon boss Jeff Bezos, to discuss the amount of tax the giant online retailer pays, and the help it might be able to offer on the environment.
Despite Amazon’s UK sales rising by 51% to almost £20bn during coronavirus lockdowns last year, it is estimated to have a tax to turnover ratio of just 0.37%.
Asked if Mr Johnson will bring up tax when he sits down with Mr Bezos, the PM’s official spokesman said: “We will very much be looking to raise that.
“We have been a lead advocate for an international solution to the tax challenges posed by digitalisation of the economy.”
