Canada – one of the few countries previously in line with Australia’s opposition to the international Green Climate Fund – now appears to have changed its mind, with Tony Abbott’s close friend prime minister Stephen Harper saying he is preparing to make a contribution.

Abbott has defied global pressure to commit to the fund, designed to help poor countries adapt to climate change, because Australia is already spending $2.5bn on its domestic Direct Action fund and providing $10bn in capital to a so-called “green bank” – which he is trying to abolish.

World leaders forced Australia to include stronger language about the Green Climate Fund in the G20 communique – and during the summit Barack Obama pledged the US would contribute $3bn to it and the Japanese prime minister, Shinzo Abe, offered $1.5bn. But soon after the conference was over Abbott indicated it would make no immediate difference to Australia’s position.

On Sunday Harper said Canada was preparing to make a contribution to the UN fund, the Globe and Mail and other Canadian media outlets reported. He did not nominate an amount.

Last November, Abbott and Harper “made history” by jointly dissenting from support for the Green Climate Fund in a communique from the Commonwealth Heads of Government meeting.

Speaking after a meeting on Sunday night with the German chancellor, Angela Merkel, Abbott said Direct Action – which funds Australia’s domestic emissions reduction, not international efforts – was already “quite a substantial fund”. He also cited the Clean Energy Finance Corporation, which he is committed to abolish.

“We also have a Clean Energy Finance Corporation which was established by the former government and there is $10bn in capital which has been allocated to this,” he said. “In addition to those two funds a proportion of our overseas aid, particularly in the Pacific, is allocated for various environmental schemes including schemes to deal with climate change. So, we are doing a very great deal and I suppose given what we are doing we don’t intend, at this time, to do more.”

Environment minister Greg Hunt tried to compare Obama’s $3bn commitment to the international fund to be spent in poor countries with Australia’s $2.5bn spending on its own domestic policy, saying that if the Direct Action fund was implemented in the US “on a like for like basis it would be the equivalent of a $25bn fund”.

Neither Abbott nor Hunt ruled out making a contribution to the fund at some time in the future and it is understood the Department of Foreign Affairs, which leads Australia’s international climate negotiations, has been considering a donation. The fund is seen as a critical part of a successful outcome at the United Nations Paris conference next year, which will discuss a global emissions pact to take effect after 2020.

But Abbott’s trenchant opposition to the fund is seen as an impediment to any contribution. He has publicly disparaged it as an international “Bob Brown bank” – another reference to the CEFC, which he wants to abolish but he also cites as evidence of Australia’s climate action.

As revealed by Guardian Australia, Abbott told world leaders at the Brisbane summit that as the leader of a major coal producer he would be “standing up for coal”.

The communique references demanded by other leaders, including Obama, were reluctantly accepted by Australia at the last minute. They included a call for contributions to the fund and for the “phasing out of inefficient fossil fuel subsidies”.

An EU spokesman reportedly described the climate negotiations with Australia as being like “trench warfare”. Other officials said it had been “very difficult” and protracted.

Speaking to the media after the summit, Abbott downplayed the importance of the fund. He took a similar line on the greenhouse reduction pledges unveiled by Obama and the Chinese president, Xi Jinping, immediately before the summit.

He said all nations “support strong action … to address climate change”, but added: “We are all going to approach this in our own way and there are a range of [climate] funds which are there.”

Obama and the UN secretary general, Ban Ki-moon, both urged G20 countries to contribute to the Green Climate Fund. In the end, at Australia’s insistence, the communique called for contributions to financing funds “such as the Green Climate Fund”.

Hunt suggested a regional rainforest fund, to which Australia recently pledged $6m, could substitute for contributions to the Green Climate Fund.