Transcript for Trump launches harsh attacks on Germany, NATO at summit

and we begin with president trump on ck. The fight beginning atreakfast today, sitting across from ams trustedie atthe nato summit. At one today, the presidasking, what'd is nato? Saying Germany is captive T Russia. Tonight, the prent's new demands now from ourallies, and you're about to heart Ver tense exchange between the Hof nato and tesident. ABC's chief foreign correspondent Terry Moran G us off from Brussels tonight. Reporter: Prent trump came here spoiling for a fig and it began immediately with a ti over breaast with nato's secretaryer, aim at one of America's closest allies. Germany, as far as I'm concerned, is captive to russia,cause it'seto much of its energy from Russia. So, we're supposed T protect Germany, but tt their energy from russia.plthat. Anan't be explaineou know that. Reporter: The president furious about a recent $12 billion gas pipeline deal Germany signed with the Kremlin. While top U.S. Officials sat there squirming, nato's chief tried efuse the moment. I think that two world wars and the cold war told us that we stronger together than apart. But how can you be together when a country is getting its energy from the person you W protection against or from the group you want protection against? Because we understand when we and together, also when dealing with Russia, we are stronger. I think what we have seen -- no, you're just ssia richer. Reporter: An astonishingly H attack, bu German chancellor Angela Merkel showed upshe took the high road. Offering a se reminder that she grew up in commu east rm under soviet domination, and that united Germany today controls its owntiny. President trump's main complaint here, the allies aren't paying ough for their own protection. Many U.S. Presidents have felt the same way, but trump is demanding allies double their comment to defense immediately. Still, it was all smiles when he met Wikel. Wve a very, very good laship with E chancellor. We have a tremendous relationship with Germany. Reporter: But nong after, a trump T, the final word attacking Germany again and nato itself. "What good is nato if ger paying Russia billions of dollars for gas energy? The is paying for Europe's protection." Wi French presidentuel macron, who's got a buddy onship withtrump, it was a very different scene. It sounded beautiful. I have no idea what he said. It sounded great. Ild say exaly the same. Repor afterward they all tried to make it look like an ordinary nato summit. The class ph all the friendly-seeming bant first lady Melania trump even chatting with mevene. Ow good the vintage, the mot this summit is sour. So, let's bring in ter Moran tonight, live from se and Terry, afterhe public fighting words Y, preside trump did eventually sign T traditional nato declaration of solidarity, affirmihat the enduring and unbreable transatlantic bon between rond North America T stand together against threats and challenges from any direction will continue. D sion was paying out on the world stage,ongress made it crystal clear where they stand. Reporter: That's T, Davi the senate yesterday, the house day, passing overwhelmingly bipartisan resolution supporting nato. E sen calling it a communityfreedom, peace, curity andred values. But all that is justpaper. The presidency is po especially in foreign policy. So, if president trump wants to rally changeamerica's relationship with nato or E take us out of T alliance, that's what's going to happen. No matter what the vintagef wine, as you pointed there at the end oourreport. Terry, thank you.

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