WASHINGTON (CNN) - Department of Homeland Security Secretary John Kelly said Tuesday that "thousands" of fighters from Syria could possibly make it to the US, though he added it wouldn't be easy, as he defended the administration's controversial travel ban executive order in front of Congress.
Under questioning from Democratic Rhode Island Rep. Jim Langevin as to whether any new information prompted the ban, Kelly said the the measure was based on concern about countries that couldn't provide adequate vetting information on potential immigrants and noted that "thousands" of Syrian fighters could possibly make it into the US. He later qualified that they would not be able to "easily" enter the US
The individuals "have the kinds of papers we have confidence could get them passed into Europe and by extension into the United States," Kelly told the House Homeland Security Committee. "We know there are thousands of fighters coming out of the caliphate that could easily -- not easily -- could bring them to Western Europe and then the United States."
Kelly did not give more details, suggesting that he had presented similar information to the committee previously in classified session and could not provide more at the public committee hearing.
Kelly was testifying before Congress for the first time since being sworn in, speaking at a hearing focusing on border security.
He faced numerous questions about President Donald Trump's controversial order -- which temporarily suspended nationals from seven high-risk countries from entering the US and put a pause on the refugee program. It has since been put on hold pending court challenges and has seen numerous walk-backs in implementation guidance, including carifying that green card holders are exempted.
"The ban was based on countries we don't have any real confidence in right now that they can help us vet people that come into the United States. Countries that are clearly in disarray," Kelly told the committee.
Kelly also took responsibility on Tuesday for the quick rollout of the executive order, saying he wished he had delayed enacting it.
Chairman Mike McCaul, a Texas Republican, told Kelly he was unhappy with some aspects of the implementation of the order, including the lack of consultation with members of Congress and reports that it was not thoroughly put through the agencies involved in putting it in place.
Kelly said he knew the order would be coming out the Friday it was signed and released late in the evening, and that he and his team had a chance to make changes the week before.
"In retrospect, I should have -- this is all on me by the way -- I should have delayed it just a bit so I could have talked to members of Congress," Kelly said.
The secretary has defended the ban despite reports that his awareness of the content was limited and that career staff at the department and others did not have opportunities to fully review the order.
"The desire was to get it out, the thinking was to get it out to quick so potentially the people were coming to harm us could not take advantage," Kelly said, echoing the Trump administration's claims that if the order was announced in advance, "bad" people could have rushed into the country.
A federal district court in Washington has blocked the order from going into effect nationwide while it works its way through the courts, and several other district courts blocked aspects of it in their jurisdiction.