Several members of the US-led coalition attacking ISIS group in Iraq and Syria are doing "nothing at all" to help destroy the jihadists, US Defense Secretary Ashton Carter said Friday.
His comments mark a departure from the Pentagon's typical depiction of the 65-member coalition, which carries the slogan "One mission, many nations," and is frequently touted to highlight global resolve in the predominantly US effort to defeat ISIS group.
"Many of them are not doing enough, or are doing nothing at all," Carter said in an interview with CNBC on the sidelines of the World Economic Forum in Davos, Switzerland. "We can do a lot ourselves ... (but) we are looking for other people to play their part."
In a separate interview with Bloomberg TV, Carter called the anti-ISIS alliance a "so-called" coalition, highlighting frustrations the Pentagon has with partners -- particularly Arab and Gulf nations -- not doing enough.
"We need others to carry their weight, there should be no free riders," he said.
Carter has spent the past week in Europe, primarily in Paris, where he sought to persuade allies to step up their efforts against ISIS group.
On Friday, he reiterated calls for one of these partners, Turkey, to bolster its fight against the jihadists.
Turkey is allowing the United States to use Incirlik, a geographically vital air base in the south, to strike ISIS targets in Iraq and Syria, but Carter said Ankara needs to do much more to secure its lengthy border with Syria.
"Turkey is a long-time friend of ours," he said during a question-and-answer session in Davos.
But "the reality is, it has a porous border for foreign fighters going in both directions. So I think the Turks could do more."
Some Arab and Gulf countries including Saudi Arabia are nominally part of the coalition, but are now more focused on fighting Iran-backed forces in Yemen.
Carter's exasperation perhaps reflects pressure from Washington, where hawkish critics say the Obama administration is moving too slowly to defeat the ISIS group.
The coalition has been bombing the jihadists since August 2014 but despite killing thousands of their fighters and reclaiming large areas they once held, the ISIS group is still launching attacks around the world, including in Jakarta, Afghanistan and Paris.
"Since no country is immune from an ISIL attack, no country can afford to ride free," Carter said in an opinion piece on Politico.com, using an alternative name for ISIS group.