CNBC takes a look at the importance of the visit for politics and the markets.

U.S. President Donald Trump is visiting Europe for the first time since taking office at a time when the markets are worried about the sustainability of his presidency.

President Trump will start his European tour in the political heart of Brussels. He is scheduled to meet with European Council President Donald Tusk and European Commission President Jean-Claude Juncker on Thursday morning.

According to Aarti Shankar, policy analyst at Open Europe, this meeting will be the "moment to see how President Trump engages with the bloc."

There have been some tensions between Europe and the U.S. since President Trump took office with the latter telling European countries they should follow the U.K.'s example and turn their back on the European institution.

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Trump's protectionist approach has also stalled negotiations on a EU-Us trade deal – the so-called TTIP (Transatlantic Trade and Investment Partnership).

Shankar told CNBC that "there might be some room to discuss trade arrangements for the future". However, above all it could be a moment "to reset" EU-U.S. relations.

Once this meeting is over, President Trump will head to NATO's headquarters, slightly outside Brussels. There, he will participate in his first NATO meeting with other heads of state. Trump has softened his stance on the transatlantic organization since calling it "obsolete" but has repeatedly demanded other NATO members to step up their contributions.

"It will be a priority for Europe to understand what role the U.S. wants to play in NATO," Shankar said. "I'm not sure if Brexit will come up," she added.