United are understood to have agreed a fee for Yanga-Mbiwa but Bernard is urging them to think again.
"Of course, but I would never have let him go," the Durham City owner told the Evening Chronicle.
"We were not strong enough to allow such a good player to go out on loan. We have been struggling at the back all season and we allow such a good player to go out on loan. I don't understand it."
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