Former Secretary of Homeland Security Jeh Johnson, an Obama appointee, said he believed President Donald Trump could be great – if he got his act together in certain arenas.

'I actually believe that Donald Trump – and I told him this when I met with him in December – I actually think Donald Trump has the potential to be a great president in a sort of Nixon goes to China way, Reagan goes to the Soviet Union way,' Johnson said today on Morning Joe.

In order to do that, however, Trump would need to 'find a way to rein in some of the more unhealthy impulses,' he's shown so far, including the tweeting, the ex-Obama official said.

Former DHS head Jeh Johnson, an Obama appointee, said today on Morning Joe that he thought President Donald Trump had 'the potential to be a great president'

Jeh Johnson (left) also outlined why he believed the U.S. had implemented a large electronics ban from eight countries, explaining the intelligence must have been 'significant'

'Listen to his staff, bring on a full compliment of political appointees who will help him govern,' Johnson included on his Trump to-do list. 'And I'm very concerned about the tweets.'

The former DHS head said he was 'very concerned' with the direction national security was going, as he feared that the country was preparing for yesterday's terror attack and not the next.

'Given where we are right now in this current environment, we need to focus on homegrown, home-born violent extremism,' Johnson said.

'That was the thing that used to keep me up at night,' he later added.

Johnson gave credence to the Department of Homeland Security decision to ban large electronics in the main cabin of commercial flights coming in from 10 airports in eight-Muslim majority countries.

ABC News reported last night that the decision for the ban came because of specific ISIS threats.

'I think it's significant,' Johnson noted.

Having left government two months ago, the ex-official said he hadn't accessed the most recent intelligence.

'But folks, aviation experts, our intelligence community, must be seeing things that are significant to prompt this action,' Johnson said.

The former DHS secretary also pointed out that the U.S. was in 'very good company,' as the British government implemented a similar policy.

'I think it's a little unfair in this context to refer to this as a ban on electronics coming from Muslim-majority countries,' Johnson added.

'We look at where the direct flights are coming from, we look at the security around the airports and we make the appropriate judgments,' he explained. 'And this judgment was almost certainly made at the TSA, DOJ intelligence community level and very often we get good cooperation from airport authorities, from security officials in these countries.'

The ban pinpoints U.S inbound flights coming from Middle Eastern and north African countries on specific carriers.

The former DHS head suggested that this new airport electronics policy was different than the Trump administration's travel ban, which is currently tied up in the courts.

Johnson's own law firm filed an amicus brief against the second iteration of the travel ban, on behalf of a number of business interests.

'It is the case that the president, the secretary of Homeland Security, has considerable legal discretion to regulate our borders,' Johnson acknowledged. 'But when you tell a judge my authority is unreviewable almost every judge will say, "We'll see."'

'So we're in this now where a matter of border security is something litigated in the courts, which many of us would have considered unprecedented as recently as a couple of months ago,' Johnson said.

'But here we are,' he added.