The Nord Stream 2 project-an $11 billion extension of the existing Nord Stream natural gas pipeline by the Kremlin-backed gas giant Gazprom and five European nations-will double Russia's gas export capability to Germany to nearly 250 billion square feet per year.
Trump has ramped up his rhetoric ahead of the talks - including in three separate tirades on Twitter on Monday and Tuesday - making the summit one of the most hard in years for the military alliance that has underpinned European security since World War II.
Trump has been criticizing North Atlantic Treaty Organisation member nations over the amount they spend on military investment.
Before he left Andrews Air Force Base, President Trump reiterated his demand for the USA to pay less and other members of the Western military alliance to pay more, and he linked the issue to the EU's trade surplus with the US.
The Prime Minister's Office said that, at the moment, no face-to-face meeting has been planned between Trudeau and Trump.
Referring to Monday's planned summit with Russian president Vladimir Putin in Helsinki, Mr Trump added: "And I have Putin".
Some NATO members point out that only 15% of America's defence spending goes on defending Europe, and that the emphasis should be on adapting NATO for new threats, not simply spending more money on defence.
"If you look at it, Germany is a captive of Russian Federation".More news: Economic Watch: US trade measures will backfire
"European troops have been fighting shoulder-to-shoulder with American soldiers in Afghanistan; 870 courageous men and women sacrificed their lives, including 40 soldiers from my homeland, Poland", said Mr. Tusk.
Trump made the comment while addressing reporters before he and First Lady Melania Trump boarded presidential helicopter Marine One.
Seated across the table from NATO Secretary General Jens Stoltenberg, Trump vented about Germany for not meeting a 2 per cent spending commitment on defense. "I think it's not". The U.S.is projected to spend 3.5 percent of GDP on defense this year, down from 3.57 percent in 2017, while Canada is forecast to reduce such spending to 1.23 percent in 2018 from 1.36 percent.
"So, we're going to have a meeting on that and the secretary general has worked very hard on that, he understands the problem and hopefully we can get it resolved".
Trump's attack comes at a time when Germany, Europe's biggest economy, spends little on defense and has a woefully unprepared and inoperable military.
"Men like him, who look after the interests of their own citizens - we could do with dozens of them in this country", Mr. Salvini said.
"Dear America, appreciate your allies, after all you don't have that many", he said. He said the United Kingdom was in "somewhat turmoil" and thinks meeting Vladimir Putin - her geopolitical enemy - will be the easiest part of his trip. "He may be the only one but that's OK with me", the president said moments before the public rebuke of Stoltenberg.
Britain's summer 2016 referendum saw the leave side prevail by a 52-48 margin - a populist victory combined with Trump's surprise victory in the US presidential race later in the year that sparked upheaval in the global order.
The 1.5 percent level forecast for NATO's European members in 2018 compares to 1.46 percent previous year, 1.44 percent in 2016 and 1.42 percent in 2015.