Europe is reckoning with a 'much more unpredictable' U.S., former EU chief says

A more "unpredictable" U.S. will only add to the challenges facing the incoming European Parliament as it navigates increasingly fraught ties with China and Russia, according to former EU Commission President José Manuel Barroso.

Barroso told CNBC on Mondaythat there was "anxiety" in Europe over the upcoming U.S. elections, reviewing how a second term for Republican presidential candidate Donald Trump could impact transatlantic relations.

"It's not just that the European Union is facing a much more aggressive Russia, a much more assertive China, it's also facing a much more unpredictable United States of America. This is the reality," Barroso told CNBC's Silvia Amaro.

The European Parliament is preparing for a new five-year term after provisional results showed record gains for the far right, even as centrist parties retained a majority in last week's EU elections. High on the agenda will be the EU's continued response to Russia's war in Ukraine, as well as navigating increasing trade tensions between the U.S. and China.

Barroso, who served as commission president from 2004 to 2014, said that the U.S. remains the EU's "biggest ally," and that the two sharing close ties, including within NATO. He nevertheless noted that the bloc was facing up to a more uncertain future.

"We are indeed very close to the United States in geopolitical terms and also in trade and investment terms," said Barroso, who is now non-executive chairman of Goldman Sachs International.

"Today there are some doubts about which way the United States can go. That's why this is translated in some anxiety, if I can put it that way," he added.

The former Portuguese prime minister noted that,"paradoxically," a more unpredictable U.S. could give Europe the necessary