A woman logs onto Facebook | Karen Bleier/AFP via Getty Images US considers asking visa applicants their social media passwords Applicants may not be let in if they fail to cooperate.

Part of U.S. President Trump's plan to subject visitors to the United States to "extreme vetting" could be to ask them for passwords to their social media accounts, Homeland Security Chief John Kelly told a congressional hearing Tuesday.

"We're looking at some enhanced or some additional screening. We may want to get on their social media, with passwords," he said.

"It's very hard to truly vet these people in these countries, the seven countries. But if they come in, we want to say, what websites do they visit, and give us your passwords. So we can see what they do on the internet."

He also indicated that applicants would not be let in if they fail to cooperate.

While Kelly stressed that no final decision has been made, he did indicate that the Trump administration intends to make the screening process a lot tougher for those wishing to enter the U.S.