United Nations leader Ban Ki-moon said in an interview published Sunday that he was optimistic the climate conference in Copenhagen that begins Monday would produce an agreement all member states would sign.

Delegates from 190 nations have descended on the Danish capital over the weekend for the UN climate change conference that ends Dec 18. The biggest climate talks in history are aimed at working out a new pact to curb global warming, replacing the 1997 Kyoto Protocol.

Over the weekend, climate activists staged protests to add pressure on leaders, including United States President Barack Obama, to agree on a strong deal.

"I am very optimistic for Copenhagen," Ban said in an interview in the Danish daily newspaper Berlingske Tidende. "We will get an agreement - and, I believe, that the agreement will be signed by all UN member states, which is historic," Ban said.

"We have the right political spirit," Ban added. "All heads of state and government have the same goal - to prevent global warming."

So far 105 world leaders have accepted the invitation, including Obama, Chinese Premier Wen Jiabao and Indian Prime Minister Manmohan Singh.

In a related development, the UN's top climate official yesterday conceded that hacked e-mails from climate scientists had damaged the image of global warming research but said evidence of a warming Earth is solid.

Yvo de Boer told the AP that the e-mails pilfered from a British university fueled skepticism among those who believe the science is manipulated to exaggerate global warming.

"I think a lot of people are skeptical about this issue in any case," de Boer said. "And then when they have the feeling ... that scientists are manipulating information in a certain direction then of course it causes concern in a number of people to say 'you see I told you so, this is not a real issue.' I think this is about the most credible piece of science that there is out there."

Tens of thousands of people joined a march in central London on Saturday calling for world leaders to agree a deal to protect the environment.

The protest was organized by a coalition of green groups and charities calling for action to prevent global temperatures from rising more than 2 degrees centigrade, seen by many scientists as the threshold for dangerous climate change.

Organizers of the Stop Climate Chaos demonstration said more than 50,000 took part. Police put the number at 20,000.

Prime Minister Gordon Brown met a delegation from the march and told them he would push for a far-reaching agreement at the Copenhagen meeting.

In another development, anti-poverty campaign group Oxfam yesterday accused European politicians of planning to "cannibalize" existing development aid budgets and repackage them as part of a deal to fight climate change.

Oxfam said it had found evidence that exposed "undercover accounting" in some rich nations' pledges to help poor nations to tackle the climate threat.

But Sweden, holder of the rotating European Union presidency, denied the charges made the day before the UN summit.

"What is new and additional money is not always clear cut, but many countries, my own included, have foreseen and planned for Copenhagen, and the money is already in state budgets," Sweden's chief climate negotiator Anders Turesson told Reuters.

Finance has emerged as one of the key obstacles in the talks to replace the Kyoto Protocol, the UN's main tool for dealing with global warming that expires in 2012.

Developing nations want billions of dollars a year to help them adapt to a problem they say was initially caused by industrialised countries. The EU says poor countries will need around 100 billion euros ($150 billion) a year by 2020, of which as much as half would come from the public purse globally.

In Japan, State Secretary for Foreign Affairs Tetsuro Fukuyama yesterday said the country would stick to its 2020 target at upcoming talks but also said that the country would consider reducing the cost burden on local CO2 emitting industries.

The comments came in the face of growing concerns among companies in Denmark that if Japan, the world's No.5 greenhouse gas emitter, promises a tough 2020 target in a deal to which other major emitting countries are not bound, it would hurt profits, in particular energy-intensive industries.

Prime Minister Yukio Hatoyama has made it clear that Japan's 2020 target to cut greenhouse gas emissions by 25 percent from 1990 levels would be applied if all major emitters, such as China and the US, agree with ambitious targets.

Fukuyama, who will attend the Copenhagen meeting, reiterated that Japan would not agree with a post-2012 deal that simply extends the Kyoto Protocol.

The US never ratified the Kyoto Protocol, which binds industrialized nations to emissions targets during its first commitment period from 2008 to 2012.