Minister of Defence Marise Payne with NATO Secretary General Jens Stoltenberg. Credit:NIDS/NATO Multimedia Library "That clearly will involve acceleration," Senator Payne said. Asked if Australia would be open to the US requiring a greater commitment from Australia, Senator Payne said "we would consider any request on its merits". Senator Payne and Mr Mattis were in Brussels for a meeting of the international Counter-IS coalition of countries involved in the fight against the terror group. The pair had a one-on-one meeting afterwards. Senator Payne said the effort to retake Mosul, for example, "has been a hard process by some very hardworking members of the Iraqi security forces, of their counterterrorism service, of their supporters in the international coalition, those who are engaged and advise and assist such as Australia.

US secretary for defence James Mattis and Defence Minister Marise Payne. Credit:US DoD "That will continue but the pace will pick up and we will see in due course - about 15 days - the final form that takes after it is presented to the president." Earlier, Mr Mattis was asked directly if additional troops would be sent to Syria. He did not directly answer the question but made it clear it was being considered as an option. "I don't know," he said "I think you'd have to ask that question of some others in order to get a full answer… right now I first want to talk to other allies and we'll decide where we're going. "Once I get current [information] and once I get allies' assumptions and appreciations for the situation we will carve out where we want to go."

Senator Payne said she would not second guess those who made operational decisions on what an acceleration of action against IS would look like. But there was a "clear mission in front of us" to complete the taking of Mosul in Iraq, she said. Then there would be work to stabilise the communities, villages and cities reclaimed from ISIS. "Then ahead of us we have to address what will be required in Raqqa [in Syria]," she said. "We will hear from the chief of the ADF and our military advisors as to how they think that plays out for us and make decisions in accord with that." NATO commitment Mr Mattis caused a stir in Brussels on Wednesday evening by threatening to "moderate" US support for NATO if other members didn't kick in more money.

He told NATO ministers that many member countries needed to significantly increase their defence spending, to the 2 per cent of GDP level agreed in 2014 but so far only implemented by a handful of members. "If your nations do not want to see America moderate its commitment to this Alliance, each of your capitals needs to show support for our common defence," Mr Mattis said. According to news reports it left some NATO officials "scared and confused" about whether the US was still fully committed to the alliance. European diplomats said if taken literally it meant American guarantees for security in Europe were not 100 per cent any more. On Thursday, Mr Mattis refused to clarify what he meant by his threat to "moderate" US support for NATO.

He said this outcome was something "that I do not anticipate ever seeing". "Sometimes you say the things you don't want to have happen, so that you head them off," he said He did say, however, that American commitment to the mutual defence pact among NATO members "remains rock solid". Senator Payne said that having met Mr Mattis she did not think he was bluffing. "I doubt that secretary Mattis bluffs," she said. "I think the observations he made were very timely… these are important undertakings and those who are sitting around the table need to step up to the plate."