"Nor should he, based on his background," Biden continued on MSNBC's "Morning Joe," referring to Trump's business experience.

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"But the thing that bothers me is I don't see any attempt for him to go out and get people who really know on the Republican side" about foreign policy, Biden added.

Following the damaging revelations in hacked Democratic National Committee (DNC) emails, Clinton's campaign has blasted Trump's warm comments about Russian President Vladimir Putin. DNC and U.S. officials have linked the hack to Russian actors.

Biden pushed back on those alleging that Trump is a "friend of Putin" but argued Trump's proposals played into the Russian president's hand.

"I don't buy that, but here's what he's doing: he's playing directly into the hands of a guy who says his overarching goal is to break up NATO and to fracture Europe," Biden said.