By slapping higher tariffs on European Union metals experts and threatening more on cars, Trump has shown his anger at the US trade deficit with the European Union.
Latvian President Raimonds Vejonis pointed out that all countries in Europe were using Russian gas.
She said it showed Britain's "steadfast commitment" to the alliance and how it can rely on the UK.
"NATO is an an alliance of 29 nations and sometimes there are differences and different views and also some disagreements, and the gas pipeline from Russian Federation to Germany is one issue where allies disagree", said Stoltenberg.
U.S. ambassador to NATO Kay Bailey Hutchison urged allies to look beyond Trump's rhetoric and focus on the summit declaration - which the United States is expected to back - which will be the basis for the alliance's work over the coming years. "And, we're going to make it fair, so that will be it". "And, dear Europe, spend more on your defense, because everyone respects an ally that is well-prepared and equipped".
Mr Trump has linked the issue of USA military spending to the EU's trade surplus with the U.S., complaining that the bloc "makes it impossible for our farmers and workers and companies to do business in Europe" and then "want us to happily defend them through Nato".
"Germany is totally controlled by Russian Federation", said Trump.
"I am very happy that today we are united in freedom, the Federal Republic of Germany. He may be the only one, but that's OK with me".
He also said while Mr Trump had very direct language on defence spending, the allies all agreed on burden sharing and 2017 saw the biggest increase in defense spending in a generation. But we can not be taken advantage of. In his tweets, the POTUS has continuously stated that the US pays too high of a price for the alliance, while our partners do not contribute enough. Other presidents has raised European defence spending levels in the past but he is intent on dealing with it.
Shortly before arriving in Brussels, Trump slammed European NATO members for failing to meet the alliance target of spending at least 2 percent of GDP on defense.
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In a White House statement, the press secretary said that the Hammonds' five-year prison sentences had been "unjust". The move by Trump raised concerns that others would be encouraged to actively oppose federal control of public land.
As you can imagine, more people are reading The Jerusalem Post than ever before.
"Dear America, appreciate your allies - after all, you don't have that many", Tusk added, and also urged European countries to "spend more on your defense because everyone respects an ally that is well-prepared and equipped".
He has sent a string of tweets over the past few days criticising the alliance - saying: "NATO must pay MORE and the United States must pay LESS".
"As far as I'm concerned, he's a competitor", he said. So I think that's inappropriate also'.
Trump has asked Europe to lower tariffs on American-made cars and other products and to buy American liquid gas.
This is not the first time Trump has taken aim at Nord Stream 2.
The US president launched a blistering attack on Germany as he stepped up demands for North Atlantic Treaty Organisation allies to contribute more to their collective defence.
But instead of trying to engage with what Trump actually said during the Fox News interview, Gardner pretended Trump actually meant the opposite of what he said. Because of that we can say that we can make our independent policies and make independent decisions.
'You tell me if that's appropriate because I think it's not.
The NATO summit is also being attended by leaders of so-called NATO partner states that are not members of the alliance. "Who would think? Who would think?" the president said outside the White House before his departure.
The NATO meeting represents the first time the two leaders have been in the same room together since the disastrous G7 summit in Charlevoix, Quebec last month - and there's no sign at all of a thaw in their chilly relationship.