The EU would lose global credibility if it fails to approve its trade deal with the Mercosur group of South American countries this week, the bloc’s top trade official said.

Italy and France want a final European Union vote on the Mercosur trade agreement to be delayed, a move that risks derailing an accord that has taken 25 years to negotiate.

Several countries warn that the holdup risks ultimately killing the trade deal, concerned that further stalling it could embolden opposition in the European Parliament or complicate next steps when Pa...