"At present, the US Department of Homeland Security and the FBI are unaware of any specific, credible threat to the US homeland from ISIS. Plainly, however, violent extremists who support ISIS have demonstrated the intent and capability to target American citizens overseas, and ISIS constitutes an active and serious threat within the region," US Secretary for Homeland Security, Jeh Johnson said in a statement.
Additionally, in response to recent threats generally from overseas, the Department of Homeland Security over the past several weeks has taken a number of steps to enhance aviation security at overseas airports with direct flights to the US and the UK and other nations have followed with similar enhancements, Johnson said.
"There is no evidence that the ISIS is taking steps to attack the United States," White House Press Secretary, Josh Earnest, told reporters at his daily news conference after the UK raised the domestic threat level from international terrorism from "Substantial" to "Severe", related to developments in Syria and Iraq.
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"This is a threat that the United States has been focused on. We've been coordinating closely with our allies, both the Brits, but others in Europe, about countering this threat and mitigating it. We've been doing that by cooperating through law enforcement channels, through national security channels, but also through intelligence channels as well," he said.
"As it relates to the United States national terror alert system, I don't anticipate at this point that there there's a plan to change that level. It is my understanding right now that there are no plans to change it," he said.
"They pose a threat because they've received military training, they are now battle hardened, and they've demonstrated a willingness to risk their lives for their cause. Those individuals have western passports, and that does give them some freedom of movement that could allow them to come back to the west and carry out acts of violence," Earnest said.