Germany has a "very high level of confidence" in European Commission President Jean-Claude Juncker despite the European Union leader's acute back pain, German government spokesman Steffen Seibert said on Friday.

Video footage of Juncker stumbling during a photo shoot at a NATO summit on Wednesday had fueled speculation over his health, with some media outlets suggesting he had been drunk.

Juncker's discomfort led the prime ministers of the Netherlands and Portugal to help him off a stage, while US President Donald Trump and British Prime Minister Theresa May stood and watched.

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'I don't think this is elegant'

But Juncker's spokesman said on Friday that the 63-year-old had been suffering from a bad case of back pain and hit back against reports about the Commission president's supposed alcoholic proclivity.

"The president on Wednesday night suffered from a very particularly painful attack of sciatica accompanied by cramps," Margaritis Schinas said. Sciatica, a lower-back nerve condition, can cause leg pain and weakness.

"I think it's more than tasteless that some press try to make insulting headlines by exploiting President Juncker's pain," Schinas added. "I don't think this is elegant and I don't think this is fair."

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Juncker known for unorthodox behavior

Schinas said Juncker, whose term will end in 2019, was taking medication and would be fit enough to attend upcoming meetings and events in China, Japan and Spain.

"He will continue to work hard, as he has been doing since the beginning of his public career," Schinas said.

Juncker has raised eyebrows in the past over his behavior at high-level meetings. In 2015, he was filmed kissing EU leaders on the head and slapping them on the stomach, chest and even the face.

amp/aw (Reuters, dpa, AFP)