ISTANBUL (AFP) - The world's top 20 economies on Tuesday expressed determination to raise global growth but struggled to overcome divisions over the most suitable methods and how best to overcome the Greek debt crisis.

Group of 20 (G-20) finance ministers and central bank chiefs meeting in Istanbul acknowledged that global economic growth remained "uneven" and the recovery "slow", especially in the euro zone and Japan as well as some emerging market economies.

They also warned of the risk of "persistent stagnation" in some leading economies due to "prolonged low inflation alongside sluggish growth."

"We are determined to overcome these challenges" to deliver sustainable growth that can create jobs and encourage inclusiveness, a key target of the Turkish G-20 presidency, they vowed in their final communique.

The G-20 states said the recent sharp decline in oil prices will provide "some boost" to global growth and should allow states to "reassess" fiscal policies to sustain economic activity.

It said that fiscal policy "has an essential role" in building confidence and sustaining domestic demand, in a prod to some states to drop their insistence on austerity.

However, there were indications of tensions that some states - notably fiscal hawk Germany - were unwilling to relax fiscal policy enough to boost demand.

US Treasury Secretary Jacob Lew said Washington wanted to see countries use all the tools at their disposal - including fiscal policy - to boost growth.

"In Europe, there's a need for more fiscal policy. There's a demand shortfall," he told reporters in Istanbul.

Lew added that the United States - currently enjoying a strong economic performance - could not alone be responsible for global growth.

"It's not going to be a good ride for the global economy if the one strong wheel is the United States," he said.

In line with agreements made during last year's Australian presidency of the G-20, members are seeking to raise global growth by at least 2 per cent and create millions of new jobs over the next four years.

IMF managing director Christine Lagarde said "time is of the essence" given the risks of persistent low growth and the high unemployment faced by many states.

NO NEW GREECE DEAL

The statement did not specifically mention Greece, which is not a member of the G-20. But the Greek debt crisis has been at the centre of bilateral talks in Istanbul ahead of a key meeting of euro zone finance ministers on Wednesday.

Greece faces a growing risk of a "miscalculation or misstep" that could spark a "very bad outcome" to the nation's debt crisis, British Finance Minister George Osborne warned in an interview with Bloomberg television in Istanbul.

German Finance Minister Wolfgang Schaeuble disappointed markets by pouring cold water on suggestions that a whole new financing package for Greece was up for discussion.

"We are not negotiating a new programme. We already have a programme," he said, adding this existing package had to be discussed before any new programme could be considered.

But Lew called for flexibility, saying a practical solution was needed that would not cause instability either in Greece or Europe.

"There should be a conversation about a pragmatic approach in which the parties can agree on terms that are mutually agreeable," he said, warning against "casual talk" on the issue.

'FIGHT TERROR FINANCING'

Amid the onslaught in Iraq and Syria by well-financed Islamic State (ISIS) militants, the G-20 also committed to "deepen our cooperation" in the fight against terrorism financing.

This would be done by exchanging information and "freezing terrorist assets".

The communique urged "all countries to speed-up their compliance with the relevant international standards" in this respect.

It said the Financial Action Task Force (FATF) against money laundering and similar bodies should "put a specific focus on financing of terrorism".

They should also develop guidelines to improve the transparency of payment systems, in order to lessen the risk they are used for the financing of terrorism and money laundering, it said.

The G-20 asked for a report by October on "proposals to strengthen all counter terrorism financing tools."