Dr. Sebastian Gorka said Wednesday he expects President Trump to continue his criticism of NATO at the 29-nation alliance's summit in Brussels. 

Trump has been outspoken about NATO, especially in the days leading up to his trip. Just hours before he took off for Europe, he tweeted that the pact is "very unfair" to the U.S.

Trump has been especially critical of NATO countries failing to fulfill their goal of spending two percent of their gross domestic products on defense by 2024. During his presidential campaign, he suggested he might only come to the defense of NATO countries that have fulfilled that obligation.

"The swamp isn't just an American phenomenon," Gorka said on "Fox & Friends."

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Gorka, who served as a deputy assistant to Trump, pointed out that Trump's trip to Europe comes as many European countries are confronted with a migrant crisis caused by open border policies.

He said German Chancellor Angela Merkel's ruling coalition is on the precipice of collapsing due to her open-door immigration policy, which has led to approximately one million refugees and asylum seekers flooding into the country in the past several years.

"Saying, 'We have no borders, let everybody in, it doesn't matter,' that has consequences, and not just national security consequences but political ones," Gorka said, adding that lax immigration policies have also created problems for leaders like U.K. Prime Minister Theresa May and French President Emmanuel Macron.

Gorka said that's why one of Trump's first actions when he took office was to sign an executive order temporarily suspending immigration from several countries with inadequate vetting systems.

"If you don't know the identity of who's coming into you country, guess what? Terrorists will use that, and they've done it," Gorka said.

Watch more from "Fox & Friends" above.

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