European Council Council Donald Tusk holds a joint press conference with the European Commission President on February 23, 2018. (JOHN THYS/AFP/Getty Images)
Washington CNN  — 

Minutes before Air Force One landed in Brussels, President Donald Trump took another poke at the European Union on Twitter.

“The European Union makes it impossible for our farmers and workers and companies to do business in Europe (U.S. has a $151 Billion trade deficit), and then they want us to happily defend them through NATO, and nicely pay for it. Just doesn’t work!” Trump wrote, likely in response to comments earlier Tuesday from European Council President Donald Tusk.

Tusk told Trump early Tuesday morning that the US “won’t have a better ally” than the EU ahead of his European trip this week.

“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,” Tusk had tweeted at Trump.

Tusk has before been a vocal critic of Trump’s rhetoric toward NATO, tweeting in May when Trump pulled out of the Iran nuclear agreement, “with friends like that, who needs enemies.” Tusk took further aim at Trump on Tuesday at a joint EU-NATO declaration, telling Trump, “it is always worth knowing who is your strategic friend and who is your strategic problem.”

Tusk also criticized Trump’s overtures towards Russia and China on Tuesday.

“I hope you have no doubt this is an investment in our security, which cannot be said with confidence about Russian & Chinese spending,” Tusk wrote.

Tusk’s tweet was a response to Trump’s recent ruminations on NATO ahead of this week’s meeting, including earlier Tuesday morning when he tweeted about US spending ahead of his departure for this year’s NATO summit in Brussels.

“The U.S. is spending many times more than any other country in order to protect them. Not fair to the U.S. taxpayer. On top of that we lose $151 Billion on Trade with the European Union. Charge us big Tariffs (& Barriers)!” Trump wrote.

Trump added, following Tusk’s tweet, “NATO countries must pay MORE, the United States must pay LESS. Very Unfair!”

Tensions are high as Trump heads back to Europe to meet with traditional American allies, some of whom were angered last month at the G7 conference in Canada.

Questions linger about a potential trade war with the EU. In the past couple of weeks, Trump has announced new tariffs against European allies and has repeatedly denounced the transatlantic alliance, increasing political pressure on NATO allies ahead of this week.

While in Europe, Trump will meet with Russian President Vladimir Putin Monday in Helsinki, Finland.

CNN’s Jeff Zeleny contributed to this report.