The G20 communique will include a significant passage on climate change, EU officials said on Sunday, as the United States and other heavyweight nations override host Australia's attempts to keep the issue off the formal agenda.

Much of the meeting of world leaders in Australia has been overshadowed by the crisis in Ukraine, with Western leaders warning Russian President Vladimir Putin that he risked more economic sanctions if he failed to end Russian backing for separatist rebels.

On Sunday, momentum swung back to other major concerns for the Group of 20 leading economies, including climate change.

That is something of an embarrassment for Australia, which had argued it was not a clear economic issue and so should not be discussed at the G20. Indeed, Prime Minister Tony Abbott has questioned the science behind climate change.

'This was really trench warfare'

"The most difficult discussion was on climate change," an EU official told reporters on condition of anonymity. "This was really trench warfare, this was really step by step by step. In the end we have references to most of the things we wanted."

The official said the passage included practical measures that countries could take and a reference to contributing to the Green Climate Fund, which U.S. President Barack Obama committed $3 billion to on Saturday.

The U.S. and Europe led the push to have climate change discussed at the meeting, with Obama using a speech on Saturday to warn that Australia's iconic Great Barrier Reef was under threat.

"Here in the Asia Pacific nobody has more at stake when it comes to thinking about and then acting on climate change," Obama said. "Here in Australia it means longer droughts, more wildfires."

Asked on Sunday if he accepted that climate change was potentially one of the biggest impediments to global economic growth, Australian Treasurer Joe Hockey said: "No. No I don't. Absolutely not."

"You just look at China. China is going to continue to increase emissions to 2030," he said. "Australia is doing the same amount of work on climate change as the United States over a 30-year period. Frankly, what we're focused on is growth and jobs."

Anti-corruption measures

EU officials said the communique, likely to be three pages, down from 27 last year, would also include an anti-corruption action plan.

China had agreed to a G20 deal aimed at cracking down on companies masking their ownership, after initial concerns about the proposal, the EU official said.

"This was difficult for China but they managed to clear that," the official said.

A working group at the Group of 20, under Australia's Attorney-General's Department, has been seeking agreement on how to improve beneficial ownership transparency and combat the use of shell companies that can hide ill-gotten money or avoid taxation. China had said on Thursday an agreement was still in discussions.

Pressure on Russia

The separatist war in eastern Ukraine, where more than 4,000 people have been killed since April, is expected to be discussed further on Sunday after a series of one-on-one meetings between Putin and leaders including Obama.

G20 summit Australia

Russian President Vladimir Putin quickly became the target of other G20 leaders as the summit began, with Stephen Harper and Australian Prime Minister Tony Abbott insisting Moscow withdraw its support for separatist rebels in eastern Ukraine. (David Gray/Reuters)

The EU has demanded Moscow withdraw troops and weapons from Ukraine and put pressure on rebels there to accept a ceasefire, after the latest fighting wrecked a truce agreed in September.

Obama, who met with key regional allies Abbott and Japanese Prime Minister Shinzo Abe early on Sunday, is due to meet with European leaders to discuss Ukraine later in the day. EU foreign ministers will meet on Monday to consider further steps, including additional possible sanctions on Russia.

Western nations have imposed successive rounds of sanctions on Moscow, accusing it of sending troops and tanks to back pro-Russian rebels fighting to break away from Ukraine. Russia denies the charges.

On Saturday, Kremlin spokesman Dmitry Peskov denied speculation that Putin would leave the summit early, saying he would take part in all G20 events.