United boss David Moyes was at the Emirates to see the 24-year-old score in the German's 2-0 first leg success over Arsenal.
Guardiola said after the midweek win in north London: "He played on a very, very high level. That was real Champions League level.
"We all want him to prolong, and he also wants that, I am very positive about it. The club, we all want that."
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