The White House on Thursday, in no uncertain terms, put the onus on the Iraqis to fight and defeat the Islamic State -- even as a new report warned foreign fighters are flocking to the battlefield at a historic and dangerous pace. 

"The United States is not going to be responsible for securing the security situation inside of Iraq," Press Secretary Josh Earnest told Fox News.

Earnest defended the administration's strategy, amid growing concerns about gains made by ISIS fighters in both Iraq and Syria. Earnest said the effort would take a "sustained commitment," but stressed that the U.S. will continue to focus on training and equipping Iraqi forces, while backing them up on the battlefield with air power. 

"Our strategy is to support the Iraqi security forces in doing what we will not do for them," he said. "The United States is prepared to train them, to equip them, and to back them on the battlefield with coalition military air power as they take the fight to ISIL in their own country." 

In saying the U.S. will not be "responsible" for the security situation, the White House was putting clear limits on the lengths to which the U.S. will go to reverse ISIS' gains, even as the Pentagon considers adjustments to the strategy. 

Former CIA Deputy Director Mike Morell countered that "it is everybody's fight." Speaking with Brian Kilmeade on Fox News Radio's "Kilmeade and Friends," Morell said the terror group poses a "significant threat to the stability of the entire Middle East." 

He said "we cannot be there forever" but urged the U.S. to play a "larger role." 

Defense Secretary Ash Carter said Thursday that U.S. military leaders are looking for ways to improve and speed up the program to train and equip Iraqi forces, including options to better prepare Sunni tribes to join the fight. 

Getting equipment to the battlefield more quickly and enhancing the training could help build the Iraqi forces' confidence, Carter said, just days after he publicly chastised them for showing "no will to fight" when they fled Ramadi last week even though they greatly outnumbered Islamic State militants. 

"One particular way that's extremely important is to involve the Sunni tribes in the fight -- that means training and equipping them," said Carter, who has tasked advisers to come up with options. 

Iraqi officials have complained that they are not getting the heavy military equipment they need fast enough. And on Tuesday President Obama said the U.S. and its allies must examine whether they are deploying military assets in Iraq effectively. A senior defense official said Carter is not considering providing weapons directly to the Sunnis, and still wants to work through the Iraqi government. 

Meanwhile, Earnest, in the interview with Fox News, also stressed the importance of continuing to go after the flow of foreign fighters and "shut down the pipeline." 

Based on a new United Nations report, however, this is a task that has grown ever-more challenging. 

The report reflected a 70 percent increase in the flow of foreign fighters in the last nine months. The report said the 25,000 fighters have been traveling to jihadi conflicts from more than 100 countries -- representing more than half the countries in the world. They are joining ISIS, Al Qaeda-aligned groups and other networks. 

"The rate of flow is higher than ever and mainly focused on [Syria and Iraq], with a growing problem also evident in Libya," the report said. 

"Such individuals and their networks pose an immediate and long-term threat. Those that have returned or will return to their States of origin or to third countries may pose a continuing threat to national and international security." 

The Analytical Support and Sanctions Monitoring Team is tasked with assessing the growth and movement of the fighters. They explained that the phenomenon of foreign fighters is not new and fighters associated with Al Qaeda can be traced to various countries, not just Afghanistan, all the way back to the 1990's. 

What is different today, the report explained, is the rapid growth in just the last year. "The overall numbers have risen sharply ...the number of countries of origin has also significantly increased." Terrorist fighters in the 1990's came from a small group of states, and now it is more than 100, "including countries that have never experienced problems with groups associated with [Al Qaeda]." 

"The problem has become an urgent global security matter," the report warned. Considering the convenience of global travel, it said, "the chance of a national of any country becoming a victim of an attack relating to foreign terrorist fighters is growing, especially with attacks targeting hotels and pubic spaces and venues." 

John Bolton, former U.S. ambassador to the U.N. under the George W. Bush administration, said the report reflected a "stunning number" of recruits. 

He told Fox News it shows "the breath of recruiting, I think, particularly for ISIS and the nature of this threat as a global growing threat." 

The Obama administration also has come under criticism lately for allegedly imposing heavy-handed rules on those involved in the air campaign against ISIS. 

Critics say the system does not allow for quick decision-making. One Navy F-18 pilot who has flown missions against ISIS voiced his frustration to Fox News, saying: "There were times I had groups of ISIS fighters in my sights, but couldn't get clearance to engage." 

Asked about the complaints on Thursday, Earnest said there are "rules of engagement," and stressed that the U.S. is "very cautious" to ensure no civilian casualties. But, he said, "This strategy, when it's been well executed, has enjoyed some success." 

Pentagon spokesman Col. Steve Warren said Thursday they are still "fine-tuning" that strategy. And as for the process for getting permission for airstrikes, he said, "We are looking to shorten the timeline." 

The Associated Press contributed to this report.