Manila: There can be no deal with Islamic State and no negotiations either, Malcolm Turnbull has declared, as the international community inches towards the unpalatable truth that a political settlement in Syria will involve talking to terrorists and may also mean leaving the "murderous tyrant" President Bashar al-Assad in place for a transitional period.

While President Assad is wanted for war crimes and responsible for the deaths of hundreds of thousands of his own people, the US, Russia, Iran, and other countries associated with the crisis are looking at some kind of power-sharing arrangement if IS can be moved to the periphery or, preferably, defeated.

Formal negotiations for that are set to commence in the new year, if a timetable agreed in Vienna recently is to be met.

Opposition Leader Bill Shorten has described the Syrian despot as "a butcher" and the Prime Minister did not quibble with that term.

"Well, he's killed, he's been responsible for killing many thousands of his citizens, so many people have described him as a butcher," Mr Turnbull said in Manila.

"I think he has been a murderous tyrant, there is no doubt about that."

Mr Shorten said the conflict in Syria is very deep and complex.

"There's a lot of deep enmities, sectarian or religious rivalries, overlaid by the rise of these terrorist organisations such as ISIL or Daesh," he said.

"I do not believe that long-term peace in Syria can be guaranteed while Assad, the 'Dutch Butcher', remains in control."

Events in Paris, following quickly from the downing of a Russian airliner over Egypt's Sinai Peninsula, have shocked the world and significantly accelerated the pace of global moves to resolve the Syrian civil war which has seen millions displaced, with 2.5 million Syrian refugees currently in Turkey alone.

Among the dearth of agreeable options is the prospect of some form of power-sharing agreement in Syria which allows the Sunni Muslim population access to proper representation and a degree of power.

But that can only occur if IS is neutralised.

Mr Turnbull, who in recent days has held one-on-one talks with leaders of countries big and small including the US and Russia, has moved to clarify what is being pursued, stressing that there will be no IS representative at the table.

"The goal here is to defeat or degrade and defeat Daesh or ISIL and there are military measures which we are undertaking and people, Australians in particular, should not forget that we are making the second largest military contribution in that theatre after the United States," he said.

"But there is also, of course, the political dimension and that is why you've seen the agreement or consensus arising out of the Vienna meeting to endeavour - I'm not suggesting this is by any means assured - but to endeavour to reach a political settlement.

"I read somewhere that someone had suggested that a political settlement would mean that Daesh would be at the table ... nobody is suggesting that, least of all me.

"Daesh or the so-called Islamic State, seeks to establish its own caliphate. It has no interest in any political settlement and I'm not aware of anyone having any interest in raising it with them. The key to a political settlement in Syria is finding a mechanism where the aggrieved Sunni majority of that country can feel included ... not 'feel' but be included in a new government which shares power between the various groups."

The reality, however, is that in the aftermath of bloody civil wars, settlements securing a lasting peace invariably involve the very pragmatism that leaders such as Mr Turnbull and his British counterpart David Cameron have urged: ie, a pragmatic and practical approach aimed at compromise.

In Afghanistan, this eventually involved what had previously been regarded as unthinkable: talking directly with the murderous 'stone-age' fanatics of the Taliban.

In Syria, while the international coalition (US, Australia, France, and 20 other countries) may yet be able to eliminate IS militarily - which few genuinely think is possible without ground troops - it would only be part of the story. There are many similarly unsavoury groups such as al-Nusra (which is sometimes called al Qaeda in Syria), with whom any peace deal would need to be brokered.

But Mr Shorten said leaving the brutal Assad regime in place would be a mistake.

"I do understand that some countries have a preference for Assad, being Russia and perhaps Iran," he said.

"But what I also understand is that you are not going to get long-term peace, you are not going to get stability or have people thinking they can have save lives in Syria or for refugees to return, while he remains in power in the long term," he said.

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