A massive party to celebrate 250 years of U.S. independence will shut one of Brussels’ most prominent public parks for up to 36 hours, test the city’s security to its limits, use facial recognition technology — and potentially harm birds.

Amid heightened tension between Europe and Donald Trump’s White House over his imposition of trade tariffs, threats to seize Greenland and the war in Iran, the scale of the undertaking on June 28 is huge. While the official guest list stands at around 5,000, roughly 8,000 invitations have been sent out, a U.S. official familiar with the planning told POLITICO. The official was granted anonymity to speak freely, as were others in this article.

In conversations with POLITICO, three U.S. officials have privately expressed doubts about whether such a logistically ambitious event, beneath the triumphal arches in Cinquantenaire Park and just a stone’s throw from the EU’s main institutions, can be pulled off. The main indoor portion of the venue, in the Autoworld museum, has a capacity of up to 1,500.

The celebration has also drawn a barrage of criticism, from local politicians and members of the European Parliament, who have questioned the timing amid strained ties between Washington and Brussels, to environmental activists worried about the impact of its planned half-hour fireworks display on the park’s swifts.