"We are investing heavily in the German armed forces and other European countries too, because the armed forces need it".
It followed an uncomfortable first round at the summit where anxious Western allies were subjected to the US president's "America first" approach.
Trump has repeatedly slammed Merkel for supporting a new pipeline that would cement Berlin's client relationship with Russian Federation and increase Moscow's influence.
He also said meeting the queen would be an experience Trump "will really cherish".More news: "Don't Look Back In Anger" - England fans' emotional praise following Croatia defeat
Invited leaders from non-NATO countries Afghanistan and Georgia were asked to leave along with most North Atlantic Treaty Organisation leaders' retinues of officials, as the heads of state and government of the Western alliance sought to deal with the man whose nation commands much of the budget and forces for Europe's defense. The resolution recognises that NATO remains the most important and critical security link between the United States and Europe and the US' commitment to the principle of collective defence as laid out in Article 5 of the NATO Treaty.
Earlier, Trump strode into NATO's new headquarters to shake hands with leaders - but only after publicly railing against Germany at a breakfast meeting with Stoltenberg.
"Based on our agreed approach of doing nothing on Ukraine without Ukraine, I wish Mr Trump well in his efforts to bring Mr Putin back into line".
Just a day ahead of the gathering, EU Council President Donald Tusk said that Trump should "acknowledge" its allies since "you do not have that many".
The defense minister agreed with Trump about defense spending.More news: 'A great meeting': Trump wants North Atlantic Treaty Organisation allies to double defence spending
"We're protecting Germany, we're protecting France, we're protecting all of these countries". "I think that two world wars and the Cold War taught us that we are stronger together than apart", he told the president, trying to calm tensions.
Stoltenberg later said Trump had "very direct language" but "when it comes to the core message we actually all agree... we have to share the burden more fairly".
European Union figures suggest Russian Federation is responsible for between 50% and 75% of Germany's gas imports, but gas makes up less than 20% of Germany's energy mix for power production. "He may be the only one, but that's OK with me".
Trump predicted as he departed Washington that the "easiest" leg of the journey would be the sit-down with Putin - a comment that did little to reassure allies fretting over his potential embrace of a Russian leader they regard as hostile.More news: New tariffs readied for Chinese goods
"Dear America, appreciate your allies, after all you don't have all that many", he said.
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