VIDEO - Sen. Chris Coons , a member of the Senate Foreign Relations Committee, joined Morning Joe to discuss President Trump's tweet to Iranian President Rouhani and Trump's general foreign policy strategy.

“The more times, the more ways that our president conducts something like diplomacy on Twitter in a way that seems unrelated to the actual reality on the ground, I think it undermines our credibility.”

On Iran and North Korea:

I’m not convinced. This seems to be the same playbook the president followed over several months with Kim Jong-un of North Korea where he threatened and threatened and threatened some sort of aggressive all-out nuclear war on Twitter and was increasingly abusive of Kim Jong-un, then did a 180-degree turn, had a handshake photo op in Singapore, which so far has had no significant outcomes. My concern is he’ll do the same, that he has now very briefly tweeted one all-caps threat at President Rouhani of the Iranian Islamic Republic and will declare himself capable of concocting some better deal. The Iran Nuclear Agreement which took years to put together and relied upon our European allies and China and Russia isn’t something you can replace with just a few tweets and photo op.

More on President Trump’s tweet:

I shake my head. I’m concerned. I frankly think we’re losing credibility internationally. The more times, the more ways that our president conducts something like diplomacy on Twitter in a way that seems unrelated to the actual reality on the ground, I think it undermines our credibility. His statement at the rally in Kansas City that Iran is now a totally different country is just obviously untrue.

On Russia:

On the Foreign Relations Committee, we’ve heard absolutely nothing that suggests Russia is making an abrupt change in its preferences as it prepares to attack our elections again in 2018. What we’ve seen across western Europe, central Europe, eastern Europe is that Russia is a persistent and aggressive adversary of democracy. It is true that in the United States in the 2016 election Russia took some actions to support both the far right and far left in order to further increase division in America, but our intelligence community unanimously assessed that in the case of the presidential election of 2016, they ultimately made a decision to support Donald Trump over Hillary Clinton and to interfere with, to attack our election to achieve that result.

On his resolution with Sen. Flake:

There’s nothing wrong with our resolution. It was dismissed last Thursday as mere symbolism and I’ll remind you that sometimes symbolism like our flag is an important rallying point for Americans. I think it is important, I believe Senator Flake thinks it’s important that the Senate speak with one voice about backing our intelligence community, federal law enforcement. But our resolution also called for action.

It called for full enforcement of the sanctions that we imposed against Russia, excuse me, that we empowered the president to impose against Russia in a 98-2 vote last year but hasn’t yet been fully imposed. It called for hearings and for the release of notes and records of the meeting in Helsinki. So, it was both important symbolism in terms of supporting the intelligence community and federal law enforcement and our resolution called for action.

What’s wrong, I think, with the Senate particularly with the Republican Caucus in the Senate, there’s some senators unwilling to do even symbolic measures that would be in any way disfavorable to the White House. That strikes me as concerning. You’ve got senior administration officials who are openly saying the opposite of what President Trump said in Helsinki. U.N. Ambassador Nikki Haley just said I believe yesterday we will never trust Vladimir Putin. If that’s the case, then why is he being invited to the White House?

On Africa:

Well, to be positive, Secretary of Commerce Ross recently led a trip to four African countries to try to strengthen and broaden our economic ties with countries that have vibrant economies and where there’s significant opportunity. And I think that is an important step forward. At the meantime, China is engaged in very active, very aggressive economic diplomacy across the continent. Xi Jinping is in southern Africa right now and just made a commitment of $14 billion in new investments in just one country in South Africa, one of Africa’s most dynamic countries with a very promising economy. My most recent meeting with the Minister of Trade of South Africa was a very somber one. Our tariffs against their steel and aluminum exports is going to have a really negative affect on our relationship with South Africa since they’re not really the country we’re trying to affect with President Trump’s tariffs, that should be focused on the U.S./China trade relationship. This is just another example of the sort of unintended harm these wildly applied and widely swung tariffs are having.