BRUSSELS (Reuters) - European Commission President Jean-Claude Juncker said he was shocked by remarks by Germany's European commissioner that offended China, gay people and French-speaking Belgians this week, but was convinced they do not represent his true views.

Juncker was commenting in his first interview on the matter since Guenther Oettinger last week called Chinese people "slit-eyes", joked about "compulsory gay marriage" and railed at a Belgian region's efforts to block an EU-Canada trade deal.

"A Commissioner cannot hold such views. I told him he had to apologize to those who could have felt targeted," Juncker said in an interview with the Belgian newspaper Le Soir on Saturday.

Oettinger apologized on Thursday, saying he realized his remarks had "hurt" people. But the long delay before he issued an apology sparked an outcry that threatened to jeopardize trade ties with China.

His U-turn came a day after the Chinese foreign ministry condemned his remarks and said they reflected a "baffling sense of superiority" among Western politicians.

Oettinger, 63, had previously accepted only that his comments on Oct. 25 had been "somewhat sloppy".

Juncker said he only learned of the comments on Wednesday night after a long holiday weekend: "I couldn't immediately turn my attention to this Oettinger's clumsiness."

But he said a conversation with the Commissioner convinced him that the comments did not represent his true opinion and that they "shared the same views".

"I sincerely think these comments did not convey his thoughts. He is a liberal man on social issues, and so I was surprised," Juncker told Le Soir.

Last Friday, before his comments had been widely reported, Juncker announced a promotion for Oettinger, who has a reputation for plain talk, from digital affairs to vice president for the budget.

The Commission is battling for public support for the European Union in the face of rising nationalist opposition exemplified by Britain's vote to leave the bloc in June.

Public outcry over Oettinger's comments comes after a scandal over whether former European Commission chief Jose Manuel Barroso broke ethics rules by taking a job at Goldman Sachs.

Juncker said in the interview he would propose extending the period during which former EU commissioners are banned from lobbying, from 18 months to three years.

"Maybe I waited too long before saying my thoughts on the ethics. The important thing is that I have drawn lessons from it for myself," Juncker said.

(Reporting by Alissa de Carbonnel; Editing by Alexander Smith)