After meeting with key allies in Paris, US Defence Secretary Ashton Carter vowed to crush what he called the IS "cancer" by "collapsing its two power centres in Raqqa and Mosul" and combating "the metastasis of the ISIL tumour worldwide."
At the same time, Russian Foreign Minister Sergei Lavrov announced Syria peace talks would start "in the next few days" after he met US Secretary of State John Kerry in Zurich.
Iran also said it would throw its weight behind a political solution, with Foreign Minister Mohammad Javad Zarif telling the World Economic Forum (WEF) in Switzerland "there is no military solution to the crisis."
Russia and Iran are accused of propping up their ally, Syrian President Bashar al-Assad, and Western powers say Moscow is indiscriminately bombing Syrian opposition forces fighting IS.
"The Russians are on the wrong track strategically and also in some cases tactically," Carter said.
"We don't have a basis for broader cooperation (with Russia)," he said.
Lavrov, by contrast, insisted Russia was willing to "more closely coordinate our actions" with the coalition to facilitate aid deliveries in Syria.
|Carter announced an unprecedented meeting of 26 defence ministers in the anti-IS coalition, plus Iraq, to be held in Brussels on February 11|
The meeting in Paris comprised defence ministers from Australia, Britain, France, Germany, Italy, the Netherlands and the US.
Carter announced an unprecedented meeting of 26 defence ministers in the anti-IS coalition, plus Iraq, to be held in Brussels on February 11 and warned he would demand greater effort.
"Every nation must come prepared to discuss further contributions to the fight," he said.
Carter has repeatedly urged other countries in the approximately 60-member coalition to step up participation in the military effort, particularly Arab and Gulf countries that are more focused on fighting Iran-backed forces in Yemen.
'Daesh is retreating'
Ministers were keen to tout progress in the campaign.
"Daesh is retreating, it is time to increase our joint efforts by implementing a coherent military strategy," French Defence Minister Jean-Yves Le Drian told reporters. Daesh is another name for IS, which is also called ISIL.
IS has lost around a quarter of its self-proclaimed caliphate, including the Iraqi city of Ramadi to US-backed local forces last month.
A Britain-based monitoring group, the Syrian Observatory for Human Rights, said on Tuesday that IS has announced plans to halve the monthly pay of its members in Syria and Iraq.
The financial strain could be a result of intensified air strikes on its oil infrastructure, a key source of revenue for the group.
Separately, Colonel Steve Warren, a Baghdad-based spokesman for the US-led anti-IS coalition, on Wednesday said nine strikes in Iraq and Syria in recent months had led to the destruction of "tens of millions" of dollars in IS cash, much of it derived from illicit oil sales.
|The Pentagon is currently pushing Iraq to launch an assault to recapture the city of Mosul from IS|
Despite some successes, the coalition faces a rapidly spreading threat around the world, notably in Libya where political chaos has allowed IS to build an estimated 3,000-strong force.
The West also lacks allies on the ground in Syria, since most opposition groups are focused on toppling Assad.
US, Australian and French instructors have already trained 15,000 Iraqi soldiers, notably against improvised explosive devices (IEDs) and vehicle suicide attacks that are the IS weapons of choice.
The Pentagon is currently pushing Iraq to launch an assault to recapture the city of Mosul from IS, and US Colonel Warren said Iraqi security forces would need help from "hundreds" of Western military trainers to do so.
But Western forces remain reluctant to get too deeply involved, fearing a repeat of the quagmire of previous campaigns in Afghanistan and Iraq.
Australia has already ruled out any increase to its military contribution, and Canada was pointedly absent from Wednesday's meeting after its new government said it would pull out of the bombing campaign.
IS showed its continued threat this week, taking 400 people hostage when it attacked the eastern Syrian town of Deir Az-zour. Some 270 have since been released.
Russia said on Wednesday it had bombed the area in the past day, and delivered 50 tonnes of humanitarian aid to the town.
The Syrian Observatory confirmed the bombings and said heavy clashes were continuing between regime and IS fighters.
Meanwhile, UN-brokered Syrian peace talks are tentatively set for next Monday in Geneva, despite disagreements over who will represent the opposition.
Syria's largest opposition coalition on Wednesday picked Islamist rebel chief Mohammad Alloush, who has the support of Saudi Arabia, but it has demanded the exclusion of other parties, including Kurdish fighters who have been one of the most capable forces against IS.