Transcript for Trump delivers statement on Syria military strike

Let's bring in our chief white house correspondent Jon Karl. Before that attack president trump consistently said Syria is not our fight. Last night he said protecting America's national security required retaliation. Reporter: It's a dramatic change in his view and his approach towards Syria and it's a change that was driven by those images that you heard him talking about, those images of the chemical weapons attack particularly the children that were killed in the attack. One image in particular, the image of a father holding his two 9-month-old twins, both killed in a chemical weapons attack. And, George, also seems to be a Dra theic change in the relations with Russia. We heard here from secretary of state Rex tillerson last night about this attack and he was especially harsh on Russia telling us either Russia has been complicit or Russia has been simply incompetent. So, we also heard from Vladimir Putin's spokesperson saying this attack has dealt a major blow to u.s./russia relations so that's another thing to watch. Right in the middle of u.s./china relations and the president meeting with the Chinese president there today in mar-a-lago. The Chinese have come out with a statement this morning urging restraint in the region but the president's action also sends a message to North Korea which is at the top of the agenda, this summit today. Reporter: No question about it, George. Another thing the secretary of state said was that this action by the president ordering this air strike demonstrates that he is willing to take action when it is called for. That willingness obviously sends a message potentially to north Korea and to the Chinese now. What the United States wants is China to take the lead on pressuring North Korea, but this sends a message that if China does not act this is a president that is willing to take matters into his own hands. Thanks very much.

This transcript has been automatically generated and may not be 100% accurate.