US could ask visa applicants for social media passwords

Visitors to the US will face tougher vetting as part of a screening process to keep out people who could pose a "security threat", Kelly said. 

He said it was one of the things under consideration especially for visitors from seven Muslim-majority countries listed on President Donald Trump's travel ban.

"We're looking at some enhanced or some additional screening," Kelly told a hearing of the House Homeland Security Committee.

"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."

"If they don't want to cooperate, then they don't come in" to the United States, he said.

Kelly stressed that no decision had been made on this, but said tighter screening was definitely in the future, even if it means longer delays for awarding US visas to visitors

"These are the things we are thinking about," he said.

"But over there we can ask them for this kind of information and if they truly want to come to America, then they will cooperate. If not, next in line."

After the executive order came into affect on January 27, reports emerged that US border officers at airports were checking travellers' Facebook accounts for political beliefs before allowing them into the country. 

Trump's ban is currently temporarily suspended under a court order.