With Trump headed for what is set to be a confrontational NATO summit, where his mission is to boost spending by other NATO members...

NATO countries must pay MORE, the United States must pay LESS. Very Unfair! — Donald J. Trump (@realDonaldTrump) July 10, 2018

... European Council President Donald Tusk told Donald Trump to stop berating NATO allies over military investment levels and to be more respectful towards America’s allies, claiming that they are now in short supply.

“Dear America, appreciate your allies, after all you don't have that many," Tusk, the former Polish prime minister, said after a signing a statement on more cooperation between the European Union and the North Atlantic Treaty Organisation, although he also accepted Europe should spend more on defense: "And, dear Europe, spend more on your defence, because everyone respects an ally that is well-prepared and equipped."

The declaration was signed ahead of the 2-day meeting of NATO members in Brussels starting Wednesday, in which Tusk and Jean-Claude Juncker, the president of the European Commission, will represent the European Union.

Trump predictably brushed aside Tusk’s criticism as he was left on the trip to Europe, which as noted before includes a NATO summit, a visit to the UK and his first dedicated bilateral meeting with Russia’s Vladimir Putin: “We do have a lot of allies, but we cannot be taken advantage of.” Before taking off for Brussels, Trump again chided fellow NATO members for not contributing enough to the alliance while maintaining a trade surplus with the United States, his latest reprimand on issues that are straining transatlantic relations.

While many U.S. presidents have urged European governments to spend more on their militaries, Trump has intensified the demands to such an extent that allies worry it could damage NATO morale and play into the hands Russian President Vladimir Putin, who they accuse of trying to divide and destabilize the West.

“Dear President Trump: America does not have, and will not have a better ally than Europe,” said Tusk, who chairs summits of EU leaders according to Reuters. “Today, Europeans (collectively) spend on defense many times more than Russia, and as much as China.” He said that money went toward both U.S. and European security when the United States regards Russia and China as threats.

Dear @realDonaldTrump. US doesn’t have and won’t have a better ally than EU. We spend on defense much more than Russia and as much as China. I hope you have no doubt this is an investment in our security, which cannot be said with confidence about Russian & Chinese spending :-) — Donald Tusk (@eucopresident) July 10, 2018

Trump’s tweet on Tuesday echoed earlier posts on Twitter on Monday and his criticism at a rally of supporters in the United States last week, in which he said that Washington was unfairly carrying almost all the cost of defending Europe.

“Getting ready to leave for Europe. First meeting - NATO. The U.S. is spending many times more than any other country in order to protect them. Not fair to the U.S. taxpayer,” Trump said.

European officials say while U.S. defense spending makes up 70 percent of combined allied governments’ military budgets, just 15 percent of U.S. expenditure is spent in Europe on NATO-related defense. Washington pays about 22 percent of the running cost of NATO, including the headquarters and commonly-funded equipment such as AWACS surveillance planes.

“On top of that we lose $151 Billion on Trade with the European Union. Charge us big Tariffs (& Barriers)!” Trump also said in the same tweet.

EU and U.S. government data put the U.S. trade deficit with the EU at around $100 billion, including services such as finance, where the United States has a surplus. EU officials also say most tariffs on U.S. goods are already low to zero.