The talks will attempt to draw up a new global climate treaty to supplant the UN's 1997 Kyoto Protocol.
Danish Prime Minister Lars Lokke Rasmussen said the involvement of heads of state and government was "crucial" to the success of the summit.
"That is why we are encouraged that already more than 60 heads of state and government have confirmed they will participate, and just as important that many more have also been positive," he told a meeting of his Liberal Party on Sunday, according to a spokesman.
Talks 'very tough'
UK Prime Minister Gordon Brown, who will be attending, has said a new deal will be more likely if heads of governments put their own reputations on the line.
Kevin Rudd on Copenhagen hopes
Australian Prime Minister Kevin Rudd, who will be a key negotiator at the summit, has said he believes those involved in the summit are capable of reaching a non-binding political agreement that would be codified sometime next year.
"I believe there is a strong and high degree of political resolve from many of the leaders around the world to land a Copenhagen agreement," he told the BBC.
But he said reaching what he called an "operational framework agreement" was "not inevitable" and that the negotiations will be "very tough".
Australia is the world's largest exporter of coal and has the highest per capita emissions of any developed nation, but Mr Rudd has said he wants to be part of the solution.
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